Bacterial efflux pump inhibitors

ABSTRACT

Disclosed herein are compounds of formula I: and salts thereof. Also disclosed are compositions comprising compounds of formula I and methods using compounds of formula I.

PRIORITY OF INVENTION

This application claims priority from United States Provisional Patent Application No. 62/470,038 that was filed Mar. 10, 2017. The entire content of the application referenced above is hereby incorporated by reference herein.

BACKGROUND OF THE INVENTION

Antibiotics have been effective tools in the treatment of infectious diseases. However, bacteria have developed several different mechanisms to overcome the action of antibiotics.

These mechanisms of resistance can be specific such as for a molecule or a family of antibiotics, or the mechanisms can be non-specific. Several mechanisms of resistance can exist in a single bacterial strain, and those mechanisms may act independently or they may act synergistically to overcome the action of an antibiotic or a combination of antibiotics. Specific mechanisms include, for example, degradation of the drug, inactivation of the drug by enzymatic modification, and alteration of the drug target. Additional mechanisms of drug resistance include mechanisms in which access of the antibiotic to the target is prevented or reduced by decreasing the transport of the antibiotic into the cell or by increasing the efflux of the drug from the cell to the outside medium. Both of these mechanisms can lower the concentration of drug at the target site and allow bacterial survival in the presence of one or more antibiotics that would otherwise inhibit or kill the bacterial cells. Some bacteria utilize both mechanisms, combining low permeability of the cell wall (including membranes) with an active efflux of antibiotics. It has been shown that efflux of antibiotics can be mediated by more than one pump in a single organism and that almost all antibiotics are subject to resistance by this mechanism.

These multiple resistance mechanisms have become widespread and threaten the clinical utility of antibacterial therapy. The increase in antibiotic resistant strains has been particularly noted in major hospitals and care centers. The consequences of the increase in resistant strains include, for example higher morbidity and mortality, longer patient hospitalization, and an increase in treatment costs. Accordingly, there is a need for agents and methods for inhibiting one or more of these mechanisms of bacterial resistance.

SUMMARY OF THE INVENTION

Compounds disclose herein, when tested in combination with a known antibiotic, lower the minimum inhibitory concentration of the known antibiotic to inhibit bacterial cell growth. Not to be bound by theory the compounds are believed to exert this effect by the inhibition of a bacterial efflux pump(s).

Accordingly, one embodiment provides a compound of formula I:

A is —C(═O)N(R^(a1))—R¹, —(C₁-C₃)alkyl-C(═O)N(R^(a1))R¹, —(C₁-C₃)alkyl-O —R¹, —O—R¹, —(C₁-C₃)alkyl-N(R^(a1))—R¹, or —N(R^(a1))—R¹;

each R¹ is independently a (C₃-C₇)carbocyclyl, (C₃-C₇)carbocyclyl-(C₁-C₄)alkyl-, 4-7 membered monocyclic heterocyclyl, or 4-7 membered monocyclic heterocyclyl-(C₁-C₄)alkyl-, wherein each (C₃-C₇)carbocyclyl or (C₃-C₇)carbocyclyl-(C₁-C₄)alkyl- is independently substituted with one or more groups (e.g., 1, 2, or 3) selected from the group consisting of Z and —(C₁-C₆)alkyl substituted with one or more Z, and wherein each 4-7 membered monocyclic heterocyclyl or 4-7 membered monocyclic heterocyclyl-(C₁-C₄)alkyl- is independently optionally substituted with one or more groups (e.g., 1, 2, or 3) selected from the group consisting of Z and —(C₁-C₆)alkyl substituted with one or more Z, wherein each Z is independently selected from the group consisting of NR^(b2)R^(c2), —NHNH₂, —C(═NR^(a2))(NR^(b2)R^(c2)), —NR^(a2)C(═NR^(a2))(R^(d2)), and —NR^(a2)C(═NR^(a2))(NR^(b2)R^(c2)) and wherein each (C₃-C₇)carbocyclyl, (C₃-C₇)carbocyclyl-(C₁-C₄)alkyl-, 4-7 membered monocyclic heterocyclyl, or 4-7 membered monocyclic heterocyclyl-(C₁-C₄)alkyl-, is independently optionally substituted independently with one or more (C₁-C₄)alkyl;

R² is hydrogen, halo, (C₁-C₄)alkyl, (C₁-C₄)haloalkyl, (C₁-C₄)alkoxy, (C₁-C₄)haloalkoxy, aryl or heteroaryl wherein the aryl or heteroaryl is optionally substituted with one or more groups independently selected from halo, —NO₂, —CN, (C₁-C₄)alkyl, (C₁-C₄)haloalkyl, (C₁-C₄)alkoxy and (C₁-C₄)haloalkoxy;

R³ is hydrogen, halo, (C₁-C₆)alkyl, (C₁-C₄)haloalkyl, (C₁-C₆)alkoxy, (C₁-C₄)haloalkoxy, aryl or heteroaryl wherein the aryl or heteroaryl is optionally substituted with one or more groups independently selected from halo, —NO₂, —CN, (C₁-C₆)alkyl, (C₁-C₄)haloalkyl, (C₁-C₆)alkoxy and (C₁-C₄)haloalkoxy;

R⁴ is hydrogen, halo, (C₁-C₆)alkyl, (C₁-C₄)haloalkyl, (C₁-C₆)alkoxy, (C₁-C₄)haloalkoxy, aryl or heteroaryl wherein the aryl or heteroaryl is optionally substituted with one or more groups independently selected from halo, —NO₂, —CN, (C₁-C₆)alkyl, (C₁-C₄)haloalkyl, (C₁-C₆)alkoxy and (C₁-C₄)haloalkoxy;

R⁵ is hydrogen, halo, (C₁-C₆)alkyl, (C₁-C₄)haloalkyl, (C₁-C₆)alkoxy, (C₁-C₄)haloalkoxy, aryl or heteroaryl wherein the aryl or heteroaryl is optionally substituted with one or more groups independently selected from halo, —NO₂, —CN, (C₁-C₆)alkyl, (C₁-C₄)haloalkyl, (C₁-C₆)alkoxy and (C₁-C₄)haloalkoxy;

R⁶ is hydrogen, halo, (C₁-C₄)alkyl, (C₁-C₄)haloalkyl, (C₁-C₄)alkoxy, (C₁-C₄)haloalkoxy, aryl or heteroaryl wherein the aryl or heteroaryl is optionally substituted with one or more groups independently selected from halo, —NO₂, —CN, (C₁-C₄)alkyl, (C₁-C₄)haloalkyl, (C₁-C₄)alkoxy and C₁-C₄)haloalkoxy;

each R^(a1) is independently hydrogen, (C₁-C₆)alkyl or (C₃-C₇)carbocyclyl;

each R^(a2) is independently hydrogen, (C₁-C₆)alkyl or (C₃-C₇)carbocyclyl;

each R^(b2) and R^(c2) is independently hydrogen, (C₁-C₆)alkyl or (C₃-C₇)carbocyclyl; and

R^(d2) is (C₁-C₆)alkyl or (C₃-C₇)carbocyclyl;

or a salt thereof.

One embodiment provides a pharmaceutical composition comprising a compound of formula I or a pharmaceutically acceptable salt thereof as described herein, and a pharmaceutically acceptable vehicle.

One embodiment provides pharmaceutical composition comprising a compound of formula I or a pharmaceutically acceptable salt thereof as described herein, one or more antibacterial agents and a pharmaceutically acceptable vehicle.

One embodiment provides a method of inhibiting a bacterial efflux pump in an animal (e.g., a mammal such as a human) comprising administering to the animal a compound of formula I or a pharmaceutically acceptable salt thereof as described herein.

One embodiment provides a method of inhibiting a bacterial efflux pump in an animal (e.g., a mammal such as a human) comprising administering to the animal in need thereof a compound of formula I or a pharmaceutically acceptable salt thereof as described herein.

One embodiment provides a method of treating or preventing a bacterial infection in an animal (e.g., a mammal such as a human) comprising co-administering to the animal a compound of formula I or a pharmaceutically acceptable salt thereof as described herein and one or more antibacterial agents.

One embodiment provides a method of treating or preventing a bacterial infection in an animal (e.g., a mammal such as a human) comprising co-administering to the animal in need thereof a compound of formula I or a pharmaceutically acceptable salt thereof as described herein and one or more antibacterial agents.

One embodiment provides a method of inhibiting a bacterial efflux pump in an animal (e.g., a mammal such as a human) with a bacterial infection comprising administering to the animal a compound of formula I or a pharmaceutically acceptable salt thereof as described herein.

One embodiment provides a method of treating or preventing a bacterial infection in an animal (e.g., a mammal such as a human) infected with bacteria comprising co-administering to the animal a compound of formula I or a pharmaceutically acceptable salt thereof as described herein and one or more antibacterial agents.

One embodiment provides a compound of formula I or a pharmaceutically acceptable salt thereof as described herein for use in medical treatment.

One embodiment provides a compound of formula I or a pharmaceutically acceptable salt thereof as described herein for the prophylactic or therapeutic inhibition of a bacterial efflux pump for the treatment of a bacterial infection.

One embodiment provides a compound of formula I or a pharmaceutically acceptable salt thereof as described herein which is used in combination with one or more antibacterial agents for the prophylactic or therapeutic treatment of a bacterial infection.

One embodiment provides the use of a compound of formula I or a pharmaceutically acceptable salt thereof as described herein for the preparation of a medicament for inhibiting a bacterial efflux pump.

One embodiment provides the use of a compound of formula I or a pharmaceutically acceptable salt thereof as described herein for the preparation of a medicament for treating a bacterial infection in an animal (e.g., a mammal such as a human).

One embodiment provides the use of a compound of formula I or a pharmaceutically acceptable salt thereof as described herein for the preparation of a medicament which is used in combination with one or more antibacterial agents for treating a bacterial infection in an animal (e.g., a mammal such as a human).

One embodiment provides processes and intermediates disclosed herein that are useful for preparing compounds of formula I or salts thereof.

DETAILED DESCRIPTION

The following definitions are used, unless otherwise described: halo or halogen is fluoro, chloro, bromo, or iodo. Alkyl and alkoxy, etc. denote both straight and branched groups but reference to an individual radical such as propyl embraces only the straight chain radical (a branched chain isomer such as isopropyl being specifically referred to).

As used herein, the term “(C_(a)-C_(b))alkyl” wherein a and b are integers refers to a straight or branched chain alkyl radical having from a to b carbon atoms. Thus when a is 1 and b is 6, for example, the term includes methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, t-butyl, n-pentyl and n-hexyl.

The term “aryl” as used herein refers to a single aromatic ring or a multiple condensed ring system wherein the ring atoms are carbon. For example, an aryl group can have 6 to 10 carbon atoms, or 6 to 12 carbon atoms. Aryl includes a phenyl radical. Aryl also includes multiple condensed ring systems (e.g., ring systems comprising 2 rings) having about 9 to 12 carbon atoms or 9 to 10 carbon atoms in which at least one ring is aromatic. Such multiple condensed ring systems may be optionally substituted with one or more (e.g., 1 or 2) oxo groups on any cycloalkyl portion of the multiple condensed ring system. It is to be understood that the point of attachment of a multiple condensed ring system, as defined above, can be at any position of the ring system including an aryl or a cycloalkyl portion of the ring. Typical aryl groups include, but are not limited to, phenyl, indenyl, naphthyl, 1, 2, 3, 4-tetrahydronaphthyl, anthracenyl, and the like.

The term “heteroaryl” as used herein refers to a single aromatic ring or a multiple condensed ring system. The term includes single aromatic rings of from about 1 to 6 carbon atoms and about 1-4 heteroatoms selected from the group consisting of oxygen, nitrogen and sulfur in the rings. The sulfur and nitrogen atoms may also be present in an oxidized form provided the ring is aromatic. Such rings include but are not limited to pyridyl, pyrimidinyl, oxazolyl or furyl. The term also includes multiple condensed ring systems (e.g. ring systems comprising 2 rings) wherein a heteroaryl group, as defined above, can be condensed with one or more heteroaryls (e.g., naphthyridinyl), heterocycles, (e.g., 1, 2, 3, 4-tetrahydronaphthyridinyl), cycloalkyls (e.g., 5,6,7,8-tetrahydroquinolyl) or aryls (e.g. indazolyl) to form a multiple condensed ring system. Such multiple condensed ring systems may be optionally substituted with one or more (e.g., 1 or 2) oxo groups on the cycloalkyl or heterocycle portions of the condensed ring. In one embodiment a monocyclic or bicyclic heteroaryl has 5 to 10 ring atoms comprising 1 to 9 carbon atoms and 1 to 4 heteroatoms. It is to be understood that the point of attachment of a multiple condensed ring system (as defined above for a heteroaryl) can be at any position of the multiple condensed ring system including a heteroaryl, heterocycle, aryl or cycloalkyl portion of the multiple condensed ring system and at any suitable atom of the multiple condensed ring system including a carbon atom and heteroatom (e.g., a nitrogen). Exemplary heteroaryls include but are not limited to pyridyl, pyrrolyl, pyrazinyl, pyrimidinyl, pyridazinyl, pyrazolyl, thienyl, indolyl, imidazolyl, oxazolyl, thiazolyl, furyl, oxadiazolyl, thiadiazolyl, quinolyl, isoquinolyl, benzothiazolyl, benzoxazolyl, indazolyl, quinoxalyl, quinazolyl, 5,6,7,8-tetrahydroisoquinolinyl, benzofuranyl, benzimidazolyl and thianaphthenyl.

The term “heterocyclyl” or “heterocycle” as used herein refers to a single saturated or partially unsaturated ring or a multiple condensed ring system. The term includes single saturated or partially unsaturated rings (e.g., 3, 4, 5, 6 or 7-membered rings) from about 1 to 6 carbon atoms and from about 1 to 3 heteroatoms selected from the group consisting of oxygen, nitrogen and sulfur in the ring. The ring may be substituted with one or more (e.g., 1, 2 or 3) oxo groups and the sulfur and nitrogen atoms may also be present in their oxidized forms. Such rings include but are not limited to azetidinyl, tetrahydrofuranyl or piperidinyl. It is to be understood that the point of attachment for a heterocycle can be at any suitable atom of the heterocycle Exemplary heterocycles include, but are not limited to aziridinyl, azetidinyl, pyrrolidinyl, piperidinyl, homopiperidinyl, morpholinyl, thiomorpholinyl, piperazinyl, tetrahydrofuranyl, dihydrooxazolyl, tetrahydropyranyl and tetrahydrothiopyranyl.

The term “haloalkyl” includes an alkyl group as defined herein that is substituted with one or more (e.g., 1, 2, 3, or 4) halo groups. One specific halo alkyl is a “(C₁-C₆)haloalkyl”.

The term cycloalkyl, carbocycle, or carbocyclyl includes saturated and partially unsaturated carbocyclic ring systems. In one embodiment the cycloalkyl is a monocyclic carbocyclic ring. Such cycloalkyls include “(C₃-C₇)carbocyclyl” and “(C₃-C₈)cycloalkyl”.

Specific values listed below for radicals, substituents, and ranges, are for illustration only; they do not exclude other defined values or other values within defined ranges for the radicals and substituents.

Specifically, (C₁-C₆)alkyl can be methyl, ethyl, propyl, isopropyl, butyl, iso-butyl, sec-butyl, pentyl, 3-pentyl, or hexyl; (C₁-C₆)alkoxy can be methoxy, ethoxy, propoxy, isopropoxy, butoxy, iso-butoxy, sec-butoxy, pentoxy, 3-pentoxy, or hexyloxy; (C₃-C₈)cycloalkyl can be cyclopropyl, cyclobutyl, cyclopentyl, or cyclohexyl; (C₁-C₆)haloalkyl can be iodomethyl, bromomethyl, chloromethyl, fluoromethyl, trifluoromethyl, 2-chloroethyl, 2-fluoroethyl, 2,2,2-trifluoroethyl, or pentafluoroethyl; aryl can be phenyl, indenyl, or naphthyl; and heteroaryl can be furyl, imidazolyl, triazolyl, triazinyl, oxazolyl, isoxazolyl, thiazolyl, isothiazoyl, pyrazolyl, pyrrolyl, pyrazinyl, tetrazolyl, pyridyl, (or its N-oxide), thienyl, pyrimidinyl (or its N-oxide), indolyl, isoquinolyl (or its N-oxide) or quinolyl (or its N-oxide).

It is to understood that the embodiments provided below are for compounds of formula I and all sub-formulas thereof (e.g., formulas Ia). It is to be understood the two or more embodiments may be combined.

In one embodiment the compound of formula I is a compound of formula Ia

or a salt thereof.

In one embodiment A is —C(═O)N(R^(a1))—R¹, —(C₁-C₃)alkyl-C(═O)N(R^(a1))R¹, —(C₁-C₃)alkyl-O—R¹, or —O—R¹.

In one embodiment A is —C(═O)N(R^(a1))—R¹.

In one embodiment A is —(C₁-C₃)alkyl-C(═O)N(R^(a1))R¹.

In one embodiment R^(a1) is hydrogen.

In one embodiment A is —O—R¹.

In one embodiment R² is hydrogen, halo, (C₁-C₄)alkyl, (C₁-C₄)haloalkyl, (C₁-C₄)alkoxy, or (C₁-C₄)haloalkoxy.

In one embodiment R² is hydrogen.

In one embodiment R³ is aryl or heteroaryl wherein the aryl or heteroaryl is optionally substituted with one or more groups independently selected from halo, —NO₂, —CN, (C₁-C₆)alkyl, (C₁-C₄)haloalkyl, (C₁-C₆)alkoxy and (C₁-C₄)haloalkoxy.

In one embodiment R³ is phenyl wherein the phenyl is optionally substituted with one or more groups independently selected from halo, —NO₂, —CN, (C₁-C₆)alkyl, (C₁-C₄)haloalkyl, (C₁-C₆)alkoxy and (C₁-C₄)haloalkoxy.

In one embodiment R³ is 4-fluorophenyl.

In one embodiment R³ is 4-fluorophenyl or 4-trifluoromethyphenyl.

In one embodiment R⁴ is hydrogen, halo, (C₁-C₆)alkyl, (C₁-C₄)haloalkyl, (C₁-C₆)alkoxy, (C₁-C₄)haloalkoxy.

In one embodiment R⁴ is hydrogen.

In one embodiment R⁵ is aryl or heteroaryl wherein the aryl or heteroaryl is optionally substituted with one or more groups independently selected from halo, —NO₂, —CN, (C₁-C₆)alkyl, (C₁-C₄)haloalkyl, (C₁-C₆)alkoxy and (C₁-C₄)haloalkoxy.

In one embodiment R⁵ is phenyl wherein the phenyl is optionally substituted with one or more groups independently selected from halo, —NO₂, —CN, (C₁-C₆)alkyl, (C₁-C₄)haloalkyl, (C₁-C₆)alkoxy and (C₁-C₄)haloalkoxy.

In one embodiment R⁵ is 4-fluorophenyl.

In one embodiment R⁵ is 4-fluorophenyl or 4-trifluoromethyphenyl.

In one embodiment R⁶ is hydrogen, halo, (C₁-C₄)alkyl, (C₁-C₄)haloalkyl, (C₁-C₄)alkoxy, or (C₁-C₄)haloalkoxy.

In one embodiment R⁶ is hydrogen.

In one embodiment the moiety:

of the compound of formula I is:

In one embodiment the moiety:

of the compound of formula I is:

In one embodiment R³ is phenyl wherein the phenyl is optionally substituted with one or more groups independently selected from halo, —NO₂, —CN, (C₁-C₆)alkyl, (C₁-C₄)haloalkyl, (C₁-C₆)alkoxy and (C₁-C₄)haloalkoxy; and R⁵ is phenyl wherein the phenyl is optionally substituted with one or more groups independently selected from halo, —NO₂, —CN, (C₁-C₆)alkyl, (C₁-C₄)haloalkyl, (C₁-C₆)alkoxy and (C₁-C₄)haloalkoxy.

In one embodiment the compound of formula I is a compound of formula Ia

wherein:

R³ is phenyl wherein the phenyl is optionally substituted with one or more groups independently selected from halo, —NO₂, —CN, (C₁-C₆)alkyl, (C₁-C₄)haloalkyl, (C₁-C₆)alkoxy and (C₁-C₄)haloalkoxy; and R⁵ is phenyl wherein the phenyl is optionally substituted with one or more groups independently selected from halo, —NO₂, —CN, (C₁-C₆)alkyl, (C₁-C₄)haloalkyl, (C₁-C₆)alkoxy and (C₁-C₄)haloalkoxy;

or a salt thereof.

In one embodiment R⁵ is 4-fluorophenyl.

In one embodiment R⁵ is 4-fluorophenyl or 4-trifluoromethyphenyl.

In one embodiment R³ is halo, (C₁-C₆)alkyl, (C₁-C₄)haloalkyl, (C₁-C₆)alkoxy, (C₁-C₄)haloalkoxy, aryl or heteroaryl wherein the aryl or heteroaryl is optionally substituted with one or more groups independently selected from halo, —NO₂, —CN, (C₁-C₆)alkyl, (C₁-C₄)haloalkyl, (C₁-C₆)alkoxy and (C₁-C₄)haloalkoxy; and R⁵ is halo, (C₁-C₆)alkyl, (C₁-C₄)haloalkyl, (C₁-C₆)alkoxy, (C₁-C₄)haloalkoxy, aryl or heteroaryl wherein the aryl or heteroaryl is optionally substituted with one or more groups independently selected from halo, —NO₂, —CN, (C₁-C₆)alkyl, (C₁-C₄)haloalkyl, (C₁-C₆)alkoxy and (C₁-C₄)haloalkoxy.

In one embodiment R³ is aryl or heteroaryl wherein the aryl or heteroaryl is optionally substituted with one or more groups independently selected from halo, —NO₂, —CN, (C₁-C₆)alkyl, (C₁-C₄)haloalkyl, (C₁-C₆)alkoxy and (C₁-C₄)haloalkoxy; and R⁵ is aryl or heteroaryl wherein the aryl or heteroaryl is optionally substituted with one or more groups independently selected from halo, —NO₂, —CN, (C₁-C₆)alkyl, (C₁-C₄)haloalkyl, (C₁-C₆)alkoxy and (C₁-C₄)haloalkoxy.

In one embodiment R³ is aryl wherein the aryl is optionally substituted with one or more groups independently selected from halo, —NO₂, —CN, (C₁-C₆)alkyl, (C₁-C₄)haloalkyl, (C₁-C₆)alkoxy and (C₁-C₄)haloalkoxy; and R⁵ is aryl wherein the aryl or heteroaryl is optionally substituted with one or more groups independently selected from halo, —NO₂, —CN, (C₁-C₆)alkyl, (C₁-C₄)haloalkyl, (C₁-C₆)alkoxy and (C₁-C₄)haloalkoxy.

In one embodiment R¹ is a 4-7 membered monocyclic heterocyclyl or 4-7 membered monocyclic heterocyclyl-(C₁-C₄)alkyl-, wherein the 4-7 membered monocyclic heterocyclyl or 4-7 membered monocyclic heterocyclyl-(C₁-C₄)alkyl- is optionally substituted independently with one or more groups selected from the group consisting of Z and —(C₁-C₆)alkyl substituted with one or more Z, wherein each Z is NR^(b2)R^(c2)nd wherein the 4-7 membered monocyclic heterocyclyl or 4-7 membered monocyclic heterocyclyl-(C₁-C₄)alkyl- is optionally substituted with one or more (C₁-C₄)alkyl.

In one embodiment R¹ is a 4-7 membered monocyclic N-heterocyclyl or 4-7 membered monocyclic N-heterocyclyl-(C₁-C₄)alkyl-, wherein the 4-7 membered monocyclic N-heterocyclyl or 4-7 membered monocyclic N-heterocyclyl-(C₁-C₄)alkyl- is optionally substituted independently with one or more groups selected from the group consisting of Z and —(C₁-C₆)alkyl substituted with one or more Z, wherein each Z is NR^(b2)R^(c2)nd wherein the 4-7 membered monocyclic N-heterocyclyl or 4-7 membered monocyclic N-heterocyclyl-(C₁-C₄)alkyl- is optionally substituted with one or more (C₁-C₄)alkyl.

In one embodiment R¹ is a pyrrolidinyl or pyrrolidinyl-(C₁-C₄)alkyl-, wherein the pyrrolidinyl or pyrrolidinyl-(C₁-C₄)alkyl- is optionally substituted independently with one or more groups selected from the group consisting of Z and —(C₁-C₆)alkyl substituted with one or more Z, wherein each Z is NR^(b2)R^(c2)nd wherein the pyrrolidinyl or pyrrolidinyl-(C₁-C₄)alkyl-is optionally substituted with one or more (C₁-C₄)alkyl.

In one embodiment R¹ is a pyrrolidinyl or pyrrolidinyl-(CH₂)—, wherein the pyrrolidinyl-(CH₂)— is optionally substituted independently with one or more groups selected from the group consisting of Z and —(C₁-C₆)alkyl substituted with one or more Z, wherein each Z is NR^(b2)R^(c2) and wherein the pyrrolidinyl or pyrrolidinyl-(C₁-C₄)alkyl-is optionally substituted with one or more (C₁-C₄)alkyl.

In one embodiment R¹ is a pyrrolidinyl or pyrrolidinyl-(CH₂)—, wherein the pyrrolidinyl-(CH₂)— is optionally substituted independently with one or more groups selected from the group consisting of Z and —(C₁-C₄)alkyl substituted with one or more Z, wherein each Z is NR^(b2)R^(c2).

In one embodiment R¹ is independently a (C₃-C₇)carbocyclyl, (C₃-C₇)carbocyclyl-(C₁-C₄)alkyl-, 4-7 membered monocyclic heterocyclyl, or 4-7 membered monocyclic heterocyclyl-(C₁-C₄)alkyl-, wherein each (C₃-C₇)carbocyclyl or (C₃-C₇)carbocyclyl-(C₁-C₄)alkyl- is independently substituted with two or more groups selected from the group consisting of Z and —(C₁-C₆)alkyl substituted with one or more Z, and wherein each 4-7 membered monocyclic heterocyclyl or 4-7 membered monocyclic heterocyclyl-(C₁-C₄)alkyl- is independently substituted with one or more groups selected from the group consisting of Z and —(C₁-C₆)alkyl substituted with one or more Z, wherein each Z is independently selected from the group consisting of NR^(b2)R^(c2), —NHNH₂, —C(═NR^(a2))(NR^(b2)R^(c2)), —NR^(a2)C(═NR^(a2))(R^(d2)), and —NR^(a2)C(═NR^(a2))(NR^(b2)R^(c2)) and wherein each (C₃-C₇)carbocyclyl, (C₃-C₇)carbocyclyl-(C₁-C₄)alkyl-, 4-7 membered monocyclic heterocyclyl, or 4-7 membered monocyclic heterocyclyl-(C₁-C₄)alkyl-, is independently optionally substituted independently with one or more (C₁-C₄)alkyl.

In one embodiment R¹ is a 4-7 membered monocyclic heterocyclyl or 4-7 membered monocyclic heterocyclyl-(C₁-C₄)alkyl-, wherein the 4-7 membered monocyclic heterocyclyl or 4-7 membered monocyclic heterocyclyl-(C₁-C₄)alkyl- is substituted independently with one or more groups selected from the group consisting of Z and —(C₁-C₆)alkyl substituted with one or more Z, wherein each Z is NR^(b2)R^(c2)nd wherein the 4-7 membered monocyclic heterocyclyl or 4-7 membered monocyclic heterocyclyl-(C₁-C₄)alkyl- is optionally substituted with one or more (C₁-C₄)alkyl.

In one embodiment R¹ is a 4-7 membered monocyclic N-heterocyclyl or 4-7 membered monocyclic N-heterocyclyl-(C₁-C₄)alkyl-, wherein the 4-7 membered monocyclic N-heterocyclyl or 4-7 membered monocyclic N-heterocyclyl-(C₁-C₄)alkyl- is substituted independently with one or more groups selected from the group consisting of Z and —(C₁-C₆)alkyl substituted with one or more Z, wherein each Z is NR^(b2)R^(c2)nd wherein the 4-7 membered monocyclic N-heterocyclyl or 4-7 membered monocyclic N-heterocyclyl-(C₁-C₄)alkyl- is optionally substituted with one or more (C₁-C₄)alkyl.

In one embodiment R¹ is a pyrrolidinyl or pyrrolidinyl-(C₁-C₄)alkyl-, wherein the pyrrolidinyl or pyrrolidinyl-(C₁-C₄)alkyl- is substituted independently with one or more groups selected from the group consisting of Z and —(C₁-C₆)alkyl substituted with one or more Z, wherein each Z is NR^(b2)R^(c2)nd wherein the pyrrolidinyl or pyrrolidinyl-(C₁-C₄)alkyl-is optionally substituted with one or more (C₁-C₄)alkyl.

In one embodiment R¹ is a pyrrolidinyl or pyrrolidinyl-(CH₂)—, wherein the pyrrolidinyl-(CH₂)— is substituted independently with one or more groups selected from the group consisting of Z and —(C₁-C₆)alkyl substituted with one or more Z, wherein each Z is NR^(b2)R^(c2) and wherein the pyrrolidinyl or pyrrolidinyl-(C₁-C₄)alkyl-is optionally substituted with one or more (C₁-C₄)alkyl.

In one embodiment R¹ is a pyrrolidinyl or pyrrolidinyl-(CH₂)—, wherein the pyrrolidinyl-(CH₂)— is substituted independently with one or more groups selected from the group consisting of Z and —(C₁-C₄)alkyl substituted with one or more Z, wherein each Z is NR^(b2)R^(c2).

In one embodiment each R^(b2) and R^(c2) is hydrogen.

In one embodiment each R^(b2) and R^(c2) is hydrogen or (C₁-C₆)alkyl

In one embodiment R¹ is:

In one embodiment R¹ is:

In one embodiment A is

In one embodiment A is:

One embodiment provides a compound that is:

or a salt thereof.

One embodiment provides a compound that is:

or a salt thereof.

One embodiment provides a salt that is:

One embodiment provides a salt that is:

One embodiment provides a method for identifying a test compound capable of inhibiting a bacterial efflux inhibitor, comprising

-   -   1) contacting bacteria with a sub-inhibitory concentration of an         antibiotic;     -   2) contacting the bacteria, either sequentially or         simultaneously, with a) an inhibitory concentration of the         antibiotic; and b) a test compound; and     -   3) quantifying the minimum inhibitory concentration (MIC) of the         antibiotic, wherein a MIC that is lower than the intrinsic MIC         of the antibiotic alone indicates the test compound is effective         to inhibit a bacterial efflux pump inhibitor.

In certain embodiments, steps 1 and 2 are separated by about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37 38, 39, 40, 41, 42, 43, 44, 45, 46, 47 or 48 hours. In certain embodiments, steps 1 and 2 are separated by about 12 hours. In certain embodiments, steps 1 and 2 are separated by about 24 hours.

One embodiment provides a method for identifying a test compound capable of inhibiting a bacterial efflux inhibitor, comprising

-   -   1) contacting bacteria with a sub-inhibitory concentration of an         antibiotic;     -   2) contacting a first subset of the bacteria with an inhibitory         concentration of the antibiotic;     -   3) contacting a second subset of the bacteria, either         sequentially or simultaneously, with a) an inhibitory         concentration of the antibiotic; and b) a test compound; and     -   4) quantifying the minimum inhibitory concentration (MIC) of the         antibiotic for the first subset of bacteria and the second         subset of bacteria, wherein a lower MIC in the second subset         indicates the test compound is effective to inhibit a bacterial         efflux pump inhibitor.

In certain embodiments, steps 1 and 2 and/or 1 and 3 are separated by about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37 38, 39, 40, 41, 42, 43, 44, 45, 46, 47 or 48 hours. In certain embodiments, steps 1 and 2 are separated by about 12 hours. In certain embodiments, steps 1 and 2 are separated by about 24 hours. In certain embodiments, steps 1 and 3 are separated by about 12 hours. In certain embodiments, steps 1 and 3 are separated by about 24 hours. In certain embodiments, steps 2 and 3 are performed at substantially the same time (e.g., at about less than 10, 30, 60, 90 or 120 seconds apart, or about 3, 4 or 5 minutes apart).

One embodiment provides a method for identifying a test compound capable of lowering the minimum inhibitory concentration (MIC) of an antibiotic, comprising

-   -   1) contacting bacteria with a sub-inhibitory concentration of         the antibiotic;     -   2) contacting the bacteria, either sequentially or         simultaneously, with a) an inhibitory concentration of the         antibiotic; and b) the test compound; and     -   3) quantifying the minimum inhibitory concentration (MIC) of the         antibiotic, wherein a MIC that is lower than the intrinsic MIC         of the antibiotic indicates the test compound is effective to         lower the MIC of the antibiotic.

In certain embodiments, steps 1 and 2 are separated by about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37 38, 39, 40, 41, 42, 43, 44, 45, 46, 47 or 48 hours. In certain embodiments, steps 1 and 2 are separated by about 12 hours. In certain embodiments, steps 1 and 2 are separated by about 24 hours.

One embodiment provides a method for identifying a test compound capable of lowering the minimum inhibitory concentration (MIC) of an antibiotic, comprising

-   -   1) contacting bacteria with a sub-inhibitory concentration of an         antibiotic;     -   2) contacting a first subset of the bacteria with an inhibitory         concentration of the antibiotic;     -   3) contacting a second subset of the bacteria, either         sequentially or simultaneously, with a) an inhibitory         concentration of the antibiotic; and b) a test compound; and     -   4) quantifying the minimum inhibitory concentration (MIC) of the         antibiotic for the first subset of bacteria and the second         subset of bacteria, wherein a lower MIC in the second subset         indicates the test compound is effective to lower the MIC of the         antibiotic.

In certain embodiments, steps 1 and 2 and/or 1 and 3 are separated by about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37 38, 39, 40, 41, 42, 43, 44, 45, 46, 47 or 48 hours. In certain embodiments, steps 1 and 2 are separated by about 12 hours. In certain embodiments, steps 1 and 2 are separated by about 24 hours. In certain embodiments, steps 1 and 3 are separated by about 12 hours. In certain embodiments, steps 1 and 3 are separated by about 24 hours. In certain embodiments, steps 2 and 3 are performed at substantially the same time (e.g., at about less than 10, 30, 60, 90 or 120 seconds apart, or about 3, 4 or 5 minutes apart).

Such methods may also be used to determine synergy between a test compound and an antibiotic.

As used herein, the term “minimum inhibitory concentration (MIC)” refers to the lowest concentration of a compound (e.g., an antibiotic) that prevents visible growth of a bacterium. Assays for measuring the MIC of a compound are known in the art, for example, as described herein. As used herein, the term “intrinsic MIC” refers the MIC of a compound (e.g., an antibiotic) for the particular bacterial species that has not been pre-exposed to the compound.

As used herein, the term “sub-inhibitory concentration” refers to a concentration of the antibiotic that does not reduce the visible growth of the bacteria. In certain embodiments, the sub-inhibitory concentration is ½×MIC of the antibiotic. In certain embodiments, the sub-inhibitory concentration of the antibiotic is a concentration that is capable of inducing the expression of one or more efflux pumps in the bacteria.

As used herein, the term “inhibitory concentration” refers to a concentration of the antibiotic that reduces the visible growth of the bacteria. In certain embodiments, this concentration is the intrinsic MIC of the antibiotic.

In certain embodiments, the bacteria are a species of bacteria described herein. In certain embodiments, the bacteria are P. aeruginosa.

In certain embodiments, the antibiotic is an antibiotic described herein. In certain embodiments, the antibiotic is cefepime, clarithromycin, or levofloxacin.

In certain embodiments, the antibiotic is a cephalosporin.

In certain embodiments, the test compound is a compound described herein, such as a compound of formula I, an efflux pump inhibitor (EPI), etc.

One embodiment provides a method of identifying a combination of a test compound and an antibiotic that is capable of treating septicemia in an animal comprising:

-   -   1) administering the test compound to the animal intravenously;     -   2) administering the antibiotic to the animal either orally or         intravenously;     -   3) administering the test compound to the animal subcutaneously;     -   4) administering the antibiotic to the animal either orally or         intravenously; and     -   5) evaluating the animal for symptoms of septicemia, wherein a         reduction in symptoms indicates the combination is effective to         treat septicemia.

In certain embodiments, each administration is independently separated by approximately about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 35, 40, 45, 50, 55 or 60 min. In certain embodiments, each administration is separated by about 5 minutes.

In certain embodiments, the method further comprises repeating steps 1-4. For example, in certain embodiments, steps 1-4 are repeated 24 hours after the antibiotic has been administered for the second time.

In certain embodiments, the combination of the test compound and antibiotic is a synergistic combination.

In certain embodiments, the animal is a non-human animal. For example, in certain embodiments, the animal is a mouse.

In certain embodiments, the antibiotic is an antibiotic described herein. In certain embodiments, the antibiotic is cefepime, clarithromycin, or levofloxacin.

In certain embodiments, the test compound is a compound described herein, such as a compound of formula I, an efflux pump inhibitor (EPI), etc.

One embodiment provides a method described herein for identifying a compound capable of inhibiting a bacterial efflux pump inhibitor (e.g., using an assay described in the Examples).

Generally, compounds of formula I as well as synthetic intermediates that can be used for preparing compounds of formula I can be prepared as illustrated in the following General Methods and Schemes. It is understood that variable groups shown below (e.g., R¹, R², R³, R⁴, R⁵, R⁶) can represent the final corresponding groups present in a compound of formula I or that these groups can represent groups that can be converted to the final corresponding groups present in a compound of formula I at a convenient point in a synthetic sequence. For example, the variable groups can contain one or more protecting groups that can be removed at a convenient point in a synthetic sequence to provide the final corresponding groups in the compound of formula I.

Generally, compounds of formula I as well as synthetic intermediates that can be used for preparing compounds of formula I can be prepared as illustrated in the following general scheme. It is understood that variable groups shown below (e.g., R², R³, R⁴, R⁵, R⁶) can represent the final corresponding groups present in a compound of formula I or that these groups can represent groups that can be converted to the final corresponding groups present in a compound of formula I at a convenient point in a synthetic sequence. For example, the variable groups can contain one or more protecting groups that can be removed at a convenient point in a synthetic sequence to provide the final corresponding groups in the compound of formula I.

Scheme 1 illustrates some a general method for the preparation of certain compounds of formula I.

(each R″ is a protecting group, hydrogen or (C₁-C₄)alkyl; W is a —(C₁-C₆)alkyl or absent; X is —(C₁-C₄)alkyl- or absent; and Y is a —(C₁-C₃)alkyl- or absent)

The compounds disclosed herein are bacterial efflux pump inhibitors. An efflux pump inhibitor is a compound that interferes with the ability of an efflux pump to export a substrate. The inhibitor may have intrinsic antibacterial properties of its own. The compounds disclosed herein may be useful for treating bacterial infections (e.g., gram negative and gram positive) when administered with an antibacterial agent.

In one embodiment the bacterial infection being treated is a Gram-negative bacterial strain infection. In one embodiment the Gram-negative bacterial strain is selected from the group consisting of Acinetobacter baumannii, Acinetobacter calcoaceticus, Acinetobacter haemolyticus, Acinetobacter baumannii, Actinobacillus actinomycetemcomitans, Aeromonas hydrophilia, Aggregatibacter actinomycetemcomitans, Agrobacterium tumefaciens, Bacteroides distasonis, Bacteroides eggerthii, Bacteroidesforsythus, Bacteroidesfragilis, Bacteroides ovalus, Bacteroides splanchnicus, Bacteroides thetaiotaomicron, Bacteroides uniformis, Bacteroides vulgaius, Bordetella bronchiseptica, Bordetella parapertussis, Bordetella pertussis, Borrelia burgdorferi, Branhamella catarrhalis, Burkholderia cepacia, Campylobacter coli, Campylobacter fetus, Campylobacter jejuni, Caulobacter crescentus, Chlamydia trachomatis, Citrobacter diversus, Citrobacter freundii, Enterobacter aerogenes, Enterobacter asburiae, Enterobacter cloacae, Enterobacter sakazakii, Escherchia coli, Francisella tularensis, Fusobacterium nucleatum, Gardnerella vaginalis, Haemophilus ducreyi, Haemophilus haemolyticus, Haemophilus influenzae, Haemophilus parahaemolyticus, Haemophilus parainfluenzae, Helicobacter pylori, Kingella denitrificans, Kingella indologenes, Kingella kingae, Kingella oralis, Klebsiella oxytoca, Klebsiella pneumoniae, Klebsiella rhinoscleromatis, Legionella pneumophila, Listeria monocytogenes, Moraxella bovis, Moraxella catarrhalis, Moraxella lacunata, Morganella morgana, Neisseria gonorrhoeae, Neisseria meningitidis, Pantoea agglomerans, Pasteurella cams, Pasteurella haemolytica, Pasteurella multocida, Pasteurella tularensis, Porphyromonas gingivalis, Proteus mirabilis, Proteus vulgaris, Providencia alcalifaciens, Providencia rettgeri, Providencia stuartii, Pseudomonas acidovorans, Pseudomonas aeruginosa, Pseudomonas alcaligenes, Pseudomonasfluorescens, Pseudomonas putida, Salmonella enteriditis, Salmonella paratyphi, Salmonella typhi, Salmonella typhimurium, Serratia marcescens, Shigella dysenteriae, Shigella jlexneri, Shigella sonnet, Stenotrophomonas maltophilla, Veillonella parvula, Vibrio cholerae, Vibrio parahaemolyticus, Yersinia enterocolitica, Yersinia intermedia, Yersinia pestis and Yersinia pseudotuberculosis.

In one embodiment the bacterial infection being treated is a Gram-positive bacterial strain infection. In one embodiment the Gram-positive bacterial strain is selected from the group consisting of Actinomyces naeslundii, Actinomyces viscosus, Bacillus anthracis, Bacillus cereus, Bacillus subtilis, Clostridium difficile, Corynebacterium diphtheriae, Corynebacterium ulcerans, Enterococcusfaecalis, Enterococcus faecium, Micrococcus luteus, Mycobacterium avium, Mycobacterium intracellulare, Mycobacterium leprae, Mycobacterium tuberculosis, Propionibacterium acnes, Staphylococcus aureus, Staphylococcus epidermidis, Staphylococcus haemolyticus, Staphylococcus hominis, Staphylococcus hyicus, Staphylococcus intermedins, Staphylococcus saccharolyticus, Staphylococcus saprophyticus, Streptococcus agalactiae, Streptococcus mutans, Streptococcus pneumoniae, Streptococcus pyogenes, Streptococcus salivarius and Streptococcus sanguis.

The compositions can, if desired, also contain other active therapeutic agents, such as a narcotic, a non-steroid anti-inflammatory drug (NSAID), an analgesic, an anesthetic, a sedative, a local anesthetic, a neuromuscular blocker, an anti-cancer, an antimicrobial (for example, an aminoglycoside, an antifungal, an antiparasitic, an antiviral, a carbapenem, a cephalosporin (e.g., cefepime), a fluoroquinolone, a macrolide, a penicillin, a sulfonamide, a tetracycline, another antimicrobial), an anti-psoriatic, a corticosteriod, an anabolic steroid, a diabetes-related agent, a mineral, a nutritional, a thyroid agent, a vitamin, a calcium-related hormone, an anti diarrheal, an anti-tussive, an anti-emetic, an anti-ulcer, a laxative, an anticoagulant, an erythropoietin (for example, epoetin alpha), a filgrastim (for example, G-CSF, Neupogen), a sargramostim (GM-CSF, Leukine), an immunization, an immunoglobulin, an immunosuppressive (for example, basiliximab, cyclosporine, daclizumab), a growth hormone, a hormone replacement drug, an estrogen receptor modulator, a mydriatic, a cycloplegic, an alkylating agent, an anti-metabolite, a mitotic inhibitor, a radiopharmaceutical, an anti-depressant, an anti-manic agent, an anti-psychotic, an anxiolytic, a hypnotic, a sympathomimetic, a stimulant, donepezil, tacrine, an asthma medication, a beta agonist, an inhaled steroid, a leukotriene inhibitor, a methylxanthine, a cromolyn, an epinephrine or analog thereof, dornase alpha (Pulmozyme), a cytokine, or any combination thereof.

In one embodiment the antibacterial agent is selected from quinolones, tetracyclines, glycopeptides, aminoglycosides, β-lactams, cephalosporins, rifamycins, macrolides, ketolides, oxazolidinones, coumermycins, and chloramphenicol.

It will be appreciated that compounds of the invention having a chiral center may exist in and be isolated in optically active and racemic forms. Some compounds may exhibit polymorphism. It is to be understood that the present invention encompasses any racemic, optically-active, polymorphic, or stereoisomeric form, or mixtures thereof, of a compound of the invention, which possess the useful properties described herein, it being well known in the art how to prepare optically active forms (for example, by resolution of the racemic form by recrystallization techniques, by synthesis from optically-active starting materials, by chiral synthesis, or by chromatographic separation using a chiral stationary phase.

When a bond in a compound formula herein is drawn in a non-stereochemical manner (e.g. flat), the atom to which the bond is attached includes all stereochemical possibilities. When a bond in a compound formula herein is drawn in a defined stereochemical manner (e.g. bold, bold-wedge, dashed or dashed-wedge), it is to be understood that the atom to which the stereochemical bond is attached is enriched in the absolute stereoisomer depicted unless otherwise noted. In one embodiment, the compound may be at least 51% the absolute stereoisomer depicted. In another embodiment, the compound may be at least 60% the absolute stereoisomer depicted. In another embodiment, the compound may be at least 80% the absolute stereoisomer depicted. In another embodiment, the compound may be at least 90% the absolute stereoisomer depicted. In another embodiment, the compound may be at least 95 the absolute stereoisomer depicted. In another embodiment, the compound may be at least 99% the absolute stereoisomer depicted.

It will also be appreciated by those skilled in the art that certain compounds of the invention can exist in more than one tautomeric form. For example, a substituent of formula —NH—C(═O)H in a compound of formula (I) could exist in tautomeric form as —N═C(OH)H. The present invention encompasses all tautomeric forms of a compound of formula I as well as mixtures thereof that can exist in equilibrium with non-charged and charged entities depending upon pH, which possess the useful properties described herein

In cases where compounds are sufficiently basic or acidic, a salt of a compound of formula I can be useful as an intermediate for isolating or purifying a compound of formula I. Additionally, administration of a compound of formula I as a pharmaceutically acceptable acid or base salt may be appropriate. Examples of pharmaceutically acceptable salts are organic acid addition salts formed with acids which form a physiological acceptable anion, for example, tosylate, methanesulfonate, acetate, citrate, malonate, tartrate, succinate, fumarate, benzoate, ascorbate, α-ketoglutarate, and α-glycerophosphate. Suitable inorganic salts may also be formed, including hydrochloride, sulfate, nitrate, bicarbonate, and carbonate salts. Salts may be obtained using standard procedures well known in the art, for example by reacting a sufficiently basic compound such as an amine with a suitable acid affording the corresponding anion. Alkali metal (for example, sodium, potassium or lithium) or alkaline earth metal (for example calcium) salts of carboxylic acids can also be made.

Pharmaceutically suitable counterions include pharmaceutically suitable cations and pharmaceutically suitable anions that are well known in the art. Examples of pharmaceutically suitable anions include, but are not limited to those described above (e.g. physiologically acceptable anions) including Cl⁻, Br⁻, I⁻, CH₃SO₃ ⁻, H₂PO₄ ⁻, CF₃SO₃ ⁻, p-CH₃C₆H₄ SO₃ ⁻, citrate, tartrate, phosphate, malate, fumarate, formate, or acetate.

It will be appreciated by those skilled in the art that a compound of the invention comprising a counterion can be converted to a compound of the invention comprising a different counterion. Such a conversion can be accomplished using a variety of well-known techniques and materials including but not limited to ion exchange resins, ion exchange chromatography and selective crystallization.

The compounds of formula I can be formulated as pharmaceutical compositions and administered to a mammalian host, such as a human patient in a variety of forms adapted to the chosen route of administration, i.e., orally or parenterally, by intravenous, intramuscular, topical or subcutaneous routes. For oral administration the compounds can be formulated as a solid dosage form with or without an enteric coating.

Thus, the present compounds may be systemically administered, e.g., orally, in combination with a pharmaceutically acceptable vehicle such as an inert diluent, excipient or an assimilable edible carrier. They may be enclosed in hard or soft shell gelatin capsules, may be compressed into tablets, or may be incorporated directly with the food of the patient's diet. For oral therapeutic administration, the active compound may be combined with one or more excipients and used in the form of ingestible tablets, buccal tablets, troches, capsules, elixirs, suspensions, syrups, wafers, and the like. Such compositions and preparations should contain at least 0.1% of active compound. The percentage of the compositions and preparations may, of course, be varied and may conveniently be between about 2 to about 90% of the weight of a given unit dosage form. The amount of active compound in such therapeutically useful compositions is such that an effective dosage level will be obtained.

The tablets, troches, pills, capsules, and the like may also contain the following: binders such as gum tragacanth, acacia, corn starch or gelatin; excipients such as dicalcium phosphate; a disintegrating agent such as corn starch, potato starch, alginic acid and the like; a lubricant such as magnesium stearate; and a sweetening agent such as sucrose, fructose, lactose or aspartame or a flavoring agent such as peppermint, oil of wintergreen, or cherry flavoring may be added. When the unit dosage form is a capsule, it may contain, in addition to materials of the above type, a liquid carrier, such as a vegetable oil or a polyethylene glycol. Various other materials may be present as coatings or to otherwise modify the physical form of the solid unit dosage form. For instance, tablets, pills, or capsules may be coated with gelatin, wax, shellac or sugar and the like. A syrup or elixir may contain the active compound, sucrose or fructose as a sweetening agent, methyl and propylparabens as preservatives, a dye and flavoring such as cherry or orange flavor. Of course, any material used in preparing any unit dosage form should be pharmaceutically acceptable and substantially non-toxic in the amounts employed. In addition, the active compound may be incorporated into sustained-release preparations, particles, and devices.

The active compound may also be administered intravenously or intramuscularly by infusion or injection. Solutions of the active compound or its salts can be prepared in water, optionally mixed with a nontoxic surfactant. Dispersions can also be prepared in glycerol, liquid polyethylene glycols, triacetin, and mixtures thereof and in oils. Under ordinary conditions of storage and use, these preparations contain a preservative to prevent the growth of microorganisms.

The pharmaceutical dosage forms suitable for injection or infusion can include sterile aqueous solutions or dispersions or sterile powders comprising the active ingredient which are adapted for the extemporaneous preparation of sterile injectable or infusible solutions or dispersions, optionally encapsulated in liposomes. In all cases, the ultimate dosage form should be sterile, fluid and stable under the conditions of manufacture and storage. The liquid carrier or vehicle can be a solvent or liquid dispersion medium comprising, for example, water, ethanol, a polyol (for example, glycerol, propylene glycol, liquid polyethylene glycols, and the like), vegetable oils, nontoxic glyceryl esters, and suitable mixtures thereof. The proper fluidity can be maintained, for example, by the formation of liposomes, by the maintenance of the required particle size in the case of dispersions or by the use of surfactants. The prevention of the action of microorganisms can be brought about by various antibacterial and antifungal agents, for example, parabens, chlorobutanol, phenol, sorbic acid, thimerosal, and the like. In many cases, it will be preferable to include isotonic agents, for example, sugars, buffers or sodium chloride. Prolonged absorption of the injectable compositions can be brought about by the use in the compositions of agents delaying absorption, for example, aluminum monostearate and gelatin.

Sterile injectable solutions are prepared by incorporating the active compound in the required amount in the appropriate solvent with various of the other ingredients enumerated above, as required, followed by filter sterilization. In the case of sterile powders for the preparation of sterile injectable solutions, the preferred methods of preparation are vacuum drying and the freeze drying techniques, which yield a powder of the active ingredient plus any additional desired ingredient present in the previously sterile-filtered solutions.

For topical administration, the present compounds may be applied in pure form, i.e., when they are liquids. However, it will generally be desirable to administer them to the skin as compositions or formulations, in combination with a dermatologically acceptable carrier, which may be a solid or a liquid.

Useful solid carriers include finely divided solids such as talc, clay, microcrystalline cellulose, silica, alumina, nanoparticles, and the like. Useful liquid carriers include water, alcohols or glycols or water-alcohol/glycol blends, in which the present compounds can be dissolved or dispersed at effective levels, optionally with the aid of non-toxic surfactants. Adjuvants such as fragrances and additional antimicrobial agents can be added to optimize the properties for a given use. The resultant liquid compositions can be applied from absorbent pads, used to impregnate bandages and other dressings, or sprayed onto the affected area using pump-type or aerosol sprayers.

Thickeners such as synthetic polymers, fatty acids, fatty acid salts and esters, fatty alcohols, modified celluloses or modified mineral materials can also be employed with liquid carriers to form spreadable pastes, gels, ointments, soaps, and the like, for application directly to the skin of the user.

Useful dosages of the compounds of formula I can be determined by comparing their in vitro activity, and in vivo activity in animal models. Methods for the extrapolation of effective dosages in mice, and other animals, to humans are known to the art; for example, see U.S. Pat. No. 4,938,949.

The amount of the compound, or an active salt or derivative thereof, required for use in treatment will vary not only with the particular salt selected but also with the route of administration, the nature of the condition being treated and the age and condition of the patient and will be ultimately at the discretion of the attendant physician or clinician.

In general, however, a suitable dose will be in the range of from about 1 to about 500 mg/kg, e.g., from about 5 to about 400 mg/kg of body weight per day, such as 1 to about 250 mg per kilogram body weight of the recipient per day.

The compound is conveniently formulated in unit dosage form; for example, containing to 500 mg, 10 to 400 mg, or 5 to 100 mg of active ingredient per unit dosage form. In one embodiment, the invention provides a composition comprising a compound of the invention formulated in such a unit dosage form.

The desired dose may conveniently be presented in a single dose or as divided doses administered at appropriate intervals, for example, as two, three, four or more sub-doses per day. The sub-dose itself may be further divided, e.g., into a number of discrete loosely spaced administrations.

Co-administration of a compound disclosed herein with one or more other active therapeutic agents (e.g., antibacterial agents) generally refers to simultaneous or sequential administration of a compound disclosed herein and one or more other active therapeutic agents, such that therapeutically effective amounts of disclosed herein and one or more other active therapeutic agents are both present in the body of the patient.

The ability of a compound disclosed herein to inhibit a bacterial efflux pump can be determined using a method like Test A or Test B as described in Example 4 and as shown in Table 1 and detailed with Example 16.

TABLE 1 Enhanced Enhanced Activity in Activity in P. Example Structure E. coli* aeruginosa** 1

  64x/6.25 μg   2x/6.25 μg 2

  8x/6.25 μg ND 3

1024x/12.5 μg    32x/12.5 μg 4

  512x/3.125 μg 64x/6.25 μg 5

1024x/6.25 μg    32x/6.25 μg 6

  32x/3.125 μg   1x/6.25 μg 7

  64x/3.125 μg   2x/6.25 μg 8

  2x/6.25 μg   1x/12.5 μg 9

—   4x/12.5 μg 10 

 512x/6.25 μg — 11 

 128x/6.25 μg — 12 

 2x/25 μg 13 

  8x/6.25 μg — 14 

  64x/6.25 μg   32x/12.5 μg *These data were generated using clarithromycin as the anitibiotic and the various EPIs against Escherichia coli ATC 25922. **These data were generated using levofloxacin as the antibiotic and the various EPIs against Pseudomonas aeruginosa ATCC 27853.

The invention will now be illustrated by the following non-limiting examples.

Preparation of Intermediates

Table 2 shows intermediates that were used or could be used to prepare compounds of described herein.

TABLE 2

Preparation of amine intermediate 1 (benzyl (2S, 4S)-2-(aminomethyl)-4-((tert-butoxycarbonyl)amino)pyrrolidine-1-carboxylate)

DIAD (0.48 g, 2.4 mmol) was added to a solution of benzyl (2S, 4S)-4-(tert-butoxycarbonyl)amino)-2-(hydroxymethyl)pyrrolidine-1-carboxylate (0.7 g, 2.0 mmol), triphenylphosphine (0.63 g, 2.4 mmol) and phthalimide (0.35 mg, 2.4 mmol) in THF (25 mL) was added at 0° C. It was stirred at 0° C. and allowed to warm to room temperature. The reaction was monitored by TLC. After the reaction was complete, it was concentrated under reduced pressure and purified by column chromatography with silica gel eluting with 10-20% ethyl acetate in hexanes to give crude product as a viscous oil (0.9 g, ˜85% purity), which was used for the next step without further purification.

Hydrazine monohydrate (0.18 mL, 3.76 mmol) was added to the solution of the above crude product (0.9 g, ˜85% purity, ˜1.88 mmol) in MeOH (30 mL). The mixture was stirred at 80° C. for 2 hours, then cooled to room temperature. The solvent was removed and the residue was triturated with CH₂Cl₂. The white solid was removed by filtration and the filtrate was concentrated under reduced pressure to give the crude product as viscous oil (0.61 g, 94% yield). ¹H NMR (300 MHz, CDCl₃) δ 7.37-7.07 (m, 5H), 6.22 (s, 1H), 4.95-4.80 (m, 2H), 4.03-3.17 (m, 4H), 2.25 (m, 1H), 1.55 (m, 2H), 1.26 (m, 9H). LC/MS: 350.20 (m+H).

Preparation of Amine Intermediate 2a and 2b (tert-butyl (((3S,5R)-5-(aminomethyl)-1-benzylpyrrolidin-3-yl)methyl)carbamate and tert-butyl (((3R,5S)-5-(aminomethyl)-1-benzylpyrrolidin-3-yl)methyl)carbamate)

tert-Butyl (((3S,5R)-5-(aminomethyl)-1-benzylpyrrolidin-3-yl)methyl)carbamate and tert-Butyl (((3R,5S)-5-(aminomethyl)-1-benzylpyrrolidin-3-yl)methyl)carbamate

DIAD (1.16 mL, 5.75 mmol) at 0° C. was added to a solution of tert-butyl (((5S)-1-benzyl-5-(hydroxymethyl)pyrrolidin-3-yl)methyl)carbamate (1.58 g, 5.23 mmol), triphenylphosphine (1.51 g, 5.75 mmol) and phthalimide (846 mg, 5.75 mmol) in THF (20 mL). It was stirred at 0° C.-room temperature and monitored by TLC. After the reaction was complete, it was concentrated under reduced pressure and purified on column chromatography with silica gel using 50-90% ethyl acetate in hexanes to give crude product as a off white solid (2.8 g, ˜80% purity). Hydrazine monohydrate (1.8 mL, 36.0 mmol) was added to the solution of the above crude product (2.8 g, ˜80% purity, ˜5.2 mmol) in MeOH (30 mL). The mixture was stirred at 80° C. for 1 hour then cooled to room temperature. The solvent was removed and the residue was triturated with CH₂Cl₂. The white solid was removed by filtration and the filtrate was concentrated under reduced pressure and purified by silica gel column chromatography. Elution with EtOAc then 1% NH₃.H₂O in 10% MeOH/CH₂Cl₂ afforded the top spot (386 mg, yellow oil, 25% yield in 2 steps) as tert-butyl (((3S,5R)-5-(aminomethyl)-1-benzylpyrrolidin-3-yl)methyl)carbamate. ¹H NMR (300 MHz, CDCl₃) δ 7.30 (m, 5H), 5.28 (br. S, 1H), 3.99 (d, J=13.5 Hz, 1H), 3.15 (d, J=12.9 Hz, 1H), 3.09 (m, 2H), 2.70-2.90 (m, 3H), 2.51 (m, 1H), 2.04-2.34 (m, 3H), 1.36-1.50 (m, 10H), and the bottom spot (498 mg, white solid, 32% yield in 2 steps) as tert-butyl (((3S,5S)-5-(aminomethyl)-1-benzylpyrrolidin-3-yl)methyl)carbamate. ¹H NMR (300 MHz, CDCl₃) δ 7.30 (m, 5H), 4.52 (br. S, 1H), 3.57 (d, J=12.9 Hz, 1H), 3.47 (d, J=12.9 Hz, 1H), 2.81-3.02 (m, 5H), 1.80-1.95 (m, 2H), 1.59 (m, 1H), 1.43 (s, 9H), 0.70 (m, 1H)

The requisite intermediates were prepared as shown in the following steps.

Step 1)

LAH (730 mg, 19.4 mmol) was added in several portions to a solution of (2S)-methyl 1-benzyl-4-cyanopyrrolidine-2-carboxylate (2.37 g mg, 9.72 mmol) in dry THF (50 mL) at 0° C. under N₂. The reaction mixture was stirred at 0° C. for 30 minutes then at room temperature for 1 hour. Then the reaction mixture was cooled to 0° C., and H₂O (0.7 mL), 15% NaOH solution (0.7 mL), EtOAc and H₂O (2.8 mL) slowly added. After stirring at room temperature for 30 min Na₂SO₄ was added. The reaction mixture was allowed to stir for 30 minutes, then the solid was removed by passing the reaction mixture through a Celite pad. The filtrate was concentrated under reduced pressure to give a crude intermediate ((2S)-4-(aminomethyl)-1-benzylpyrrolidin-2-yl)methanol. The crude intermediate was not further purified and identified. It was directly used in next step. The above intermediate was dissolved in methylene chloride (30 mL) then it was added Boc₂O (2.54 g, 11.7 mmol) and TEA (2.02 mL, 14.6 mmol). The reaction mixture was stirred at room temperature overnight. The reaction mixture was diluted with methylene chloride and washed with water, brine then dried over anhydrous sodium sulfate. The solvent was removed and the residue was purified by column chromatography on silica gel using EtOAc. The desired product was collected (1.58 g, 54% yield) as light yellow oil. ¹H NMR (300 MHz, CDCl₃) δ 7.30 (m, 5H), 4.84 (br. S, 1H), 3.98 (d, J=13.5 Hz, 1H), 3.72 (m, 1H), 3.48 (d, J=11.1 Hz, 1H), 3.26 (d, J=12.9 Hz, 1H), 3.07 (m, 2H), 2.73 (m, 2H), 2.43 (m, 1H), 2.26 (m, 1H), 2.10 (m, 1H), 1.60 (m, 2H), 1.42 (s, 9H).

Preparation of amine intermediate 3 (tert-butyl (2-((3S,5S)-5-(aminomethyl)-1-benzylpyrrolidin-3-yl)propan-2-yl)carbamate)

Hydrazine monohydrate (10 mg, 0.23 mmol) was added to a solution of tert-butyl (2-((3S,5S)-1-benzyl-5-((1,3-dioxoisoindolin-2-yl)methyl)pyrrolidin-3-yl)propan-2-yl)carbamate (55 mg, 0.12 mmol) in EtOH (4 mL). The mixture was stirred at room temperature and the precipitate formed was filtered off and washed with ethanol. The filtrate was concentrated under reduced pressure and diluted with EtOAc, washed with saturated NaHCO₃ and brine sequentially. The organic layer was dried over anhydrous sodium sulfate and concentrated under reduced pressure. The crude product (40 mg, 98% yield) was used directly without further purification. ¹H NMR (300 MHz, CD₃OD) δ 7.24 (m, 5H), 6.03 (br, 1H), 4.56 (d, J=12.9 Hz, 1H), 3.17 (d, J=12.9 Hz, 1H), 2.86 (d, J=10.5 Hz, 1H), 2.77 (m, 1H), 2.43 (m, 1H), 2.23 (m, 1H), 2.12 (m, 1H), 1.95 (m, 1H), 1.62 (m, 2H), 1.37 (s, 9H), 1.21 (s, 3H), 1.14 (s, 3H).

The requisite intermediates were prepared as shown in the following steps.

Step 1)

LiBH₄ (360 mg, 16.4 mmol) was added in several portions to a solution of (2S)-methyl 1-benzyl-4-cyanopyrrolidine-2-carboxylate (2.0 g mg, 8.2 mmol) in dry THF (30 mL). The reaction mixture was stirred at 80° C. for 1 hour then cooled to 0° C. Acetone (1.0 mL) was added slowly to the reaction mixture to quench the reaction. After stirring at room temperature for 30 minutes, the solvent was removed to give a residue. The residue was dissolved in EtOAc and washed with water, saturated NaHCO₃, and brine. The organic layer was dried over anhydrous sodium sulfate and filtered. The filtrate was concentrated under reduced pressure and purified on silica gel to give the product (1.33 g, 75% yield) as colorless oil. ¹H NMR (300 MHz, CDCl₃) δ 7.30 (m, 5H), 4.02 (d, J=13.5 Hz, 1H), 3.77 (m, 1H), 3.50 (m, 1H), 3.40 (d, J=13.5 Hz, 1H), 3.22 (m, 1H), 2.96 (m, 1H), 2.81 (m, 1H), 2.58 (m, 1H), 2.35 (m, 1H), 2.28 (m, 1H).

Step 2);

Imidazole (472 mg, 6.94 mmol), and TBDPSCl (1.33 mL, 5.10 mmol) was added to a solution of tert (5S)-1-benzyl-5-(hydroxymethyl)pyrrolidine-3-carbonitrile (1.0 g, 4.63 mmol) in CH₂Cl₂ (10 mL). The above reaction mixture was stirred at room temperature overnight, then diluted with CH₂Cl₂ and washed with water, saturated NaHCO₃ and brine. The organic layer was dried over anhydrous sodium sulfate and filtered. The filtrate was concentrated under reduced pressure and purified on silica gel to give the desired product (1.81 g, 86% yield). ¹H NMR (300 MHz, CD₃Cl) δ 7.67 (m, 4H), 7.40 (m, 6H), 7.26 (m, 5H), 4.04 (d, J=13.5 Hz, 1H), 3.79 (m, 1H), 3.67 (m, 1H), 3.34 (d, J=13.5 Hz, 1H), 3.15 (m, 1H), 2.92 (m, 1H), 2.80 (m, 1H), 2.50 (m, 1H), 2.37 (m, 1H), 2.10 (m, 1H), 1.16 (s, 9H).

Step 3)

MeLi (1.6M in hexane, 3.7 mL, 6 mmol) solution) was slowly added dropwise to anhydrous CeCl₃ (1.63 g, 6.6 mmol) in THF (12 mL) and it was stirred at room temperature for 2 hour then it was put in a dry ice-acetone bath. The color of reaction mixture changed to yellow. It was stirred at −78° C. for 0.5 hour then the solution of (3S,5S)-1-benzyl-5-(((tert-butyldiphenylsilyl)oxy)-methyl)pyrrolidine-3-carbonitrile (0.91 g, 2 mmol) in THF (3 mL) was added slowly. The reaction mixture was stirred at −78° C. for 3 hour. Crude ¹HNMR showed the presence of the desired product. It was quenched with ammonia (1 mL), then extracted with EtOAc, dried over anhydrous Na₂SO₄ and concentrated under reduced pressure to give the product as a colorless oil (0.826 g, 85% yield), which was used for next step reaction without purification. ¹H NMR (300 MHz, CDCl₃) δ 7.88 (m, 5H), 7.43 (m, 5H), 7.27 (m, 5H), 4.14 (d, J 20=13.5 Hz, 1H), 3.83 (m, 1H), 3.66 (m, 1H), 3.19 (d, J=13.5 Hz, 1H), 2.78 (m, 2H), 2.59 (m, 1H), 2.01 (m, 2H), 1.42 (m, 1H), 1.05 (s, 9H), 1.01 (s, 3H).

Step 4)

Boc₂O (0.74 g, 3.4 mmol) and DIPEA (0.6 mL, 3.4 mmol) was added to a solution of (3S,5S)-1-benzyl-5-(((tert-butyldiphenyl silyl)oxy)methyl)pyrrolidine-3-carbonitrile (0.82 g, 1.68 mmol) in methylene chloride (20 mL). It was stirred at room temperature, overnight and TLC showed no starting material left. It was washed with water, brine and dried over anhydrous sodium sulfate. The crude product was purified by column chromatography on silica gel using 0-10% EtOAc in hexane. A colorless powder was collected (0.95 g, 96% yield). ¹H NMR (300 MHz, CDCl₃) δ 7.68 (m, 5H), 7.40 (m, 5H), 7.33 (m, 5H), 6.09 (br, 1H), 4.25 (d, J=13.5 Hz, 1H), 3.80 (m, 1H), 3.70 (m, 1H), 3.06 (d, J=13.5 Hz, 1H), 2.87 (d, J=9.9 Hz, 1H), 2.58 (m, 1H), 2.03 (m, 2H), 1.69 (m, 2H), 1.42 (s, 9H), 1.25 (s, 3H), 1.16 (s, 3H), 1.06 (s, 9H).

Step 5)

TBAF solution in THF (1.0 M, 8 mL, 8 mmol) was added to a solution of tert-butyl (2-((3S,5S)-1-benzyl-5-(((tert-butyldiphenylsilyl)oxy)methyl)pyrrolidin-3-yl)propan-2-yl)carbamate (0.93 g, 1.58 mmol) in THF (15 mL). It was stirred at room temperature until no starting material was left. The crude product was purified by column chromatography on silica gel using 30-50% EtOAc in hexane. A colorless oil was collected (0.405 g, 74% yield). ¹H NMR (300 MHz, CDCl₃) δ 7.26 (m, 5H), 6.03 (br, 1H), 3.95 (d, J=12.9 Hz, 1H), 3.68 (dd, J=3.0, 10.5 Hz, 1H), 3.46 (d, J=10.5 Hz, 1H), 3.24 (d, J=12.9 Hz, 1H), 3.17 (d, J=12.9 Hz, 1H), 2.82 (m, 1H), 2.76 (m, 1H), 2.44 (m, 1H), 2.35 (m, 1H), 1.84 (t, J=8.1 Hz, 2H), 1.18 (m, 1H), 0.98 (s, 6H), 0.87 (m, 1H).

Step 6)

DIAD (73 mg, 0.24 mmol) at 0° C. was added to a solution of tert-butyl (2-((AV)-1-benzyl-5-(hydroxymethyl)pyrrolidin-3-yl)propan-2-yl)carbamate (105 mg, 0.3 mmol), triphenylphosphine (94 mg, 0.36 mmol) and phthalimide (53 mg, 0.36 mmol) in THF (5 mL). It was stirred at 0° C. and allowed to warm to room temperature. The reaction was monitored by TLC. After the reaction was complete, the reaction mixture was concentrated under reduced pressure and purified by column chromatograph with silica gel using 50-90% ethyl acetate in hexanes to give product as a white solid (60 mg, 42% yield)¹H NMR (300 MHz, CDCl₃) δ 7.84 (m, 2H), 7.74 (m, 2H), 7.29 (m, 5H), 5.77 (br, 1H), 4.56 (d, J=13.2 Hz, 1H), 3.86 (m, 2H), 3.17 (d, J=13.2 Hz, 1H), 2.86 (d, J=8.1 Hz, 1H), 2.77 (m, 1H), 2.19 (m, 1H), 2.16 (m, 1H), 2.04 (m, 1H), 1.78 (m, 1H), 1.37 (s, 9H), 1.12 (s, 6H).

EXAMPLES Example 1. Preparation of N-(((2S, 4S)-4-aminopyrrolidin-2-yl)methyl)-4,4″-difluoro-[1, 1′:3′, 1′-terphenyl]-5′-carboxamide dihydrochloride

Pd/C (10%, 20 mg) was added to a solution of benzyl (2S, 4S)-4-((tert-butoxycarbonyl)amino)-2-(4,4″-difluoro-[1, 1′:3′, 1′-terphenyl]-5′-carboxamido)methyl)pyrrolidine-1-carboxylate (100 mg, 0.16 mmol) in methanol (10 mL). It was stirred under H₂ overnight. The solid was filtered off through a Celite pad and the filtrate was concentrated under reduced pressure to give a residue. The residue was dissolved in MeOH (1 mL) was added HCl solution in dioxane (4 M, 0.1 mL) and it was stirred at room temperature overnight then concentrated under reduced pressure. The crude product was triturated with EtOAc and the white solid was collected by filtration to provide the title compound as white solid (65 mg, 85% yield in two steps). LC/MS: 408.30 (M+H).

The requisite intermediate was prepared as described in the following paragraph.

DIPEA (0.112 mL, 0.64 mmol), HOBt (21 mg, 0.155 mmol) and EDC (58 mg, 0.31 mmol) were added to a solution of 4,4″-difluoro-[1,1′:3′,1″-terphenyl]-5′-carboxylic acid (72 mg, 0.23 mmol) in dry DMF (1.5 mL). The reaction mixture was stirred at room temperature and benzyl (2S,4S)-2-(aminomethyl)-4-((tert-butoxycarbonyl)amino)pyrrolidine-1-carboxylate (amine intermediate 1) (90 mg, 0.26 mmol) was added. The reaction mixture was stirred at room temperature overnight. It was diluted with EtOAc and washed with water and brine. The organic layer was dried over anhydrous sodium sulfate and filtered. The filtrate was concentrated under reduced pressure and purified by column chromatography on silica gel using 30-40% EtOAc in hexane to give the product (110 mg, 66% yield) as a white solid. ¹H NMR (300 MHz, CDCl₃) δ 8.48 (s, 1H), 8.06 (s, 1H), 7.86 (s, 1H), 7.71-7.62 (m, 5H), 7.34-7.21 (m, 4H), 7.19-7.16 (m, 4H), 5.16 (m, 2H), 4.26 (m, 1H), 4.16 (m, 1H), 3.98 (m, 2H), 3.58 (m, 1H), 3.38 (m, 1H), 2.46 (m, 1H), 1.43 (m, 9H)

Example 2. Preparation of N-(((2S, 4S)-4-aminopyrrolidin-2-yl)methyl)-2-4,4″-difluoro-[1, 1′:3′, 1′-terphenyl]-5′-yl)-2-methylpropanamide dihydrochloride

Pd/C (10%, 20 mg) was added to a solution of benzyl (2S, 4S)-4-((tert-butoxycarbonyl)amino)-2-((2-(4,4″-difluoro-[1, 1′:3,1′-terphenyl]-5′-yl)-2-methylpropanamido)methyl)pyrrolidine-1-carboxylate (100 mg, 0.14 mmol) in methanol (10 mL). It was stirred under H₂ overnight. The solid was filtered off through a Celite pad and the filtrate was concentrated under reduced pressure to give a residue. The residue was dissolved in MeOH (1 mL) was added HCl solution in dioxane (4 M, 0.1 mL). It was stirred at room temperature overnight then concentrated under reduced pressure. The crude product was triturated with EtOAc and the white solid was collected by filtration to provide the title compound as white solid (67 mg, 92% yield). ¹H NMR (300 MHz, DMSO) δ 9.88 (bs, 1H), 9.32 (bs, 1H), 8.55 (bs, 4H), 8.0 (m, 1H), 7.86-7.81 (m, 3H), 7.75 (s, 1H), 7.56 (s, 2H), 7.55-7.32 (m, 4H), 3.88 (m, 1H), 3.66 (m, 1H), 3.51-3.45 (m, 2H), 2.39 (m, 2H), 1.8 (m, 1H), 1.64 (s, 6H).

The requisite intermediates were prepared as described in the following paragraphs.

Step 1)

The mixture of methyl 2-(3, 5-dibromophenyl)-2-methylpropanoate (0.5 g, 1.5 mmol) in 1,4-dioxane (20 mL) 2 N Na₂CO₃ (5.0 mL), 4-fluorophenylboronic acid (1.9 g, 13.3 mmol), tetrakis(triphenyl-phosphine)palladium (0.2 g) was degassed with N₂, then heated to reflux for 16 hours. The reaction mixture was worked up with ethyl acetate (60 mL) and brine (30 mL×2) to give a dark paste. The paste was purified on ISCO (40 g silica) with ethyl acetate (0˜10%)/hexanes to give the product as a pale yellow solid. The solid was dissolved into THF/H₂O (10 mL, 4:1) and LiOH—H₂O (0.27 g, 6.4 mmol), and the mixture was stirred at room temperature for 16 hours. The reaction mixture was acidified with IN HCl, and worked up with ethyl acetate (30 mL) and brine (20 mL×2) to give the product (2-(4,4″-difluoro-[1,1′:3′,1″-terphenyl]-5′-yl)-2-methylpropanoic acid) as a beige solid (0.45 g, 80% yield). 1H NMR (CDCl₃, 300 MHz): δ 7.61-7.56 (m, 5H), 7.44 (m, 2H), 7.15 (m, 4H), 1.58 (bs, 6H).

Step 2)

DIPEA (0.10 mL, 0.57 mmol), HOBt (32 mg, 0.14 mmol) and EDC (53 mg, 0.23 mmol) were added to a solution of 2-(4,4″-difluoro-[1,1′:3′,1′-terphenyl]-5′-yl)-2-methylpropanoic acid (81 mg, 0.23 mmol) in dry DMF (1.5 mL). The reaction mixture was stirred at room temperature and (amine intermediate 1) (80 mg, 0.23 mmol) was added. The reaction mixture was stirred at room temperature overnight. It was diluted with EtOAc and washed with water and brine. The organic layer was dried over anhydrous sodium sulfate and filtered. The filtrate was concentrated under reduced pressure and purified by column chromatography on silica gel using 30-40% EtOAc in hexane to give the product (105 mg, 66% yield) as a white solid. ¹H NMR (300 MHz, CDCl₃) δ 7.74-7.55 (m, 7H), 7.35-7.28 (m, 4H), 7.21-7.15 (m, 5H), 6.73 (bs, 1H), 5.21 (bs, 1H), 5.06-4.94 (m, 2H), 4.08 (m, 1H), 3.92-3.88 (m, 2H), 3.64 (m, 1H), 3.33 (m, 1H), 3.13 (m, 1H), 2.28 (m, 1H), 1.47 (m, 9H), 1.43 (m, 3H), 1.33 (m, 3H).

Example 3, Preparation of N-(((2S)-4-(2-aminopropan-2-yl)pyrrolidin-2-yl)methyl)-4,4″-difluoro-[1,1′:3′, 1″-terphenyl]-5′-carboxamide dihydrochloride

Pd/C (10%, 20 mg) was added to a solution tert-butyl (2-((5S)-1-benzyl-5-((4,4″-difluoro-[1,1′:3′,1″-terphenyl]-5′-ylcarboxamido)methyl)pyrrolidin-3-yl)propan-2-yl)carbamate (24 mg, 0.04 mmol) in methanol (5 mL) was added. The reaction mixture was stirred under H₂ overnight. The solid was filtered off through a pad of Celite and concentrated under reduced pressure to provide a residue, which was dissolved in (MeOH (1 mL) was added HCl solution (4 N in dioxane, 0.2 mL). It was stirred at room temperature overnight and solvent was removed under reduced pressure. The residue was triturated with EtOAc and the product was collected as a white powder (11 mg, 56% yield in 2 steps). ¹H NMR (300 MHz, CD₃OD) δ 8.13 (s, 2H), 8.01 (s, 1H), 7.80 (m, 4H), 7.22 (m, 4H), 4.00 (m, 1H), 3.83 (m, 2H), 3.52 (m, 2H), 2.80 (m, 1H), 2.35 (m, 1H), 1.80 (m, 1H), 1.40 (s, 6H).

The requisite intermediate was prepared as described in the following paragraph.

DIPEA (0.035 ml, 0.2 mmol), HOBt (10 mg, 0.07 mmol), EDC (19 mg, 0.1 mmol) were added to a solution of 4,4″-difluoro-[1,1′:3′,1″-terphenyl]-5′-carboxylic acid (31 mg, 0.1 mmol) in DMF (0.5 mL). The reaction mixture was stirred at room temperature then tert-butyl (2-((5S)-5-(aminomethyl)-1-benzylpyrrolidin-3-yl)propan-2-yl)carbamate (30 mg, 0.09 mmol) was added and the reaction was stirred at room temperature overnight. The reaction mixture was diluted with EtOAc. The combined organic layer was washed with water and then brine, dried over anhydrous sodium sulfate and filtered. The filtrate was then concentrated under reduced pressure and purified by column chromatography on silica gel to give the product (24 mg, 44% yield) as a white solid. ¹H NMR (300 MHz, CDCl₃) δ 8.04 (m, 2H), 7.82 (m, 1H), 7.0 (m, 4H), 7.22-7.02 (m, 9H), 4.85 (br, 1H), 4.13 (m, 1H), 3.84 (m, 1H), 3.68 (m, 1H), 3.38 (m, 1H), 3.20 (m, 1H), 3.01 (m, 1H), 2.85 (m, 1H), 2.14 (m, 1H), 1.74 (m, 1H), 1.36 (s, 9H), 1.26 (s, 3H), 1.24 (s, 3H).

Example 4, Preparation of N-(((2S,4R)-4-(aminomethyl)pyrrolidin-2-yl)methyl)-4,4″-difluoro-[1,1′:3′,1″-terphenyl]-5′-carboxamide dihydrochloride

Pd/C (10%, 50 mg) was added to a solution of tert-butyl (((3R,5S)-1-benzyl-5-((4,4″-difluoro-[1,1′:3′, 1″-terphenyl]-5′-ylcarboxamido)methyl)pyrrolidin-3-yl)methyl)carbamate (220 mg, 0.36 mmol) in methanol (15 mL). The reaction mixture was stirred under H₂ overnight. The solid was filtered off through a Celite pad and the filtrate was concentrated under reduced pressure to give a residue. The residue was dissolved in MeOH (3 mL) was added HCl solution in dioxane (4 M, 0.4 mL) and it was stirred at room temperature for 1 hour then concentrated under reduced pressure. The crude product was triturated with EtOAc and the white solid was collected by filtration to provide the title compound (100 mg, 56% yield in two steps). ¹H NMR (300 MHz, DMSO) δ 9.50 (m, 1H), 9.31 (m, 1H), 8.89 (d, J=8.4 Hz, 1H), 8.06 (m, 5H), 7.88 (m, 4H), 7.34 (m, 4H), 4.28 (m, 1H), 2.92-2.51 (m, 5H), 2.33-2.13 (m, 3H), 1.36 (m, 1H).

The requisite intermediate was prepared as described in the following paragraph.

DIPEA (0.19 mL, 1.1 mmol), HOBt (45 mg, 0.33 mmol) and EDC (125 mg, 0.65 mmol) were added to a solution of 4,4″-difluoro-[1,1′:3′,1″-terphenyl]-5′-carboxylic acid (186 mg, 0.6 mmol) in dry DMF (5 mL). The reaction mixture was stirred at room temperature for 5 minutes and tert-butyl (((3R,5S)-5-(aminomethyl)-1-benzylpyrrolidin-3-yl)methyl)carbamate amine intermediate 2a (174 mg, 0.55 mmol) was added. The reaction was continued to stir at room temperature overnight. It was then diluted with EtOAc and washed with water and brine. The organic layer was dried over anhydrous sodium sulfate and filtered. The filtrate was concentrated under reduced pressure and purified on silica gel to give the product (240 mg, 72% yield) as a white solid. ¹H NMR (300 MHz, CDCl₃) δ 7.84 (m, 2H), 7.79 (m, 1H), 7.63-7.58 (m, 4H), 7.30 (m, 5H), 7.19-7.13 (m, 4H), 6.17 (m, 1H), 4.56 (m, 1H), 4.28 (m, 1H), 3.56 (s, 2H), 3.19-2.90 (m, 3H), 2.83 (m, 1H), 2.15 (m, 1H), 1.94-1.77 (m, 2H), 1.40 (s, 9H), 1.06 (m, 1H).

Example 5, Preparation of N-(((2S,4S)-4-(aminomethyl)pyrrolidin-2-yl)methyl)-4,4″-difluoro-[1,1′:3′,1″-terphenyl]-5′-carboxamide dihydrochloride

Pd/C (10%, 40 mg) was added to a solution of tert-butyl (((3S,5S)-1-benzyl-5-((4,4″-difluoro-[1,1′:31″-terphenyl]-5′-ylcarboxamido)methyl)pyrrolidin-3-yl)methyl)carbamate (120 mg, 0.20 mmol) in methanol (10 mL). The reaction mixture was stirred under H₂ overnight. The solid was filtered off through a Celite pad and the filtrate was concentrated under reduced pressure to give a residue. The residue was dissolved in MeOH (2 mL) and a HCl solution in dioxane (4 N, 0.3 mL) was added. The reaction mixture was stirred at room temperature overnight then concentrated under reduced pressure. The crude product was triturated with EtOAc and the white solid was collected by filtration to provide the title compound (41 mg, 41% yield in two steps). ¹H NMR (300 MHz, DMSO) δ 9.39 (m, 1H), 9.12 (m, 2H), 8.02-7.77 (m, 10H), 7.21 (m, 4H), 3.75-3.50 (m, 3H), 3.10-2.70 (m, 3H), 2.33-2.13 (m, 3H), 1.35 (m, 1H).

The requisite intermediate was prepared as described in the following paragraph.

DIPEA (0.14 mL, 0.78 mmol), HOBt (32 mg, 0.24 mmol) and EDC (90 mg, 0.47 mmol) were added to a solution of 4,4″-difluoro-[1,1′:3′,1″-terphenyl]-5′-carboxylic acid (133 mg, 0.43 mmol) in dry DMF (3 mL). The reaction mixture was stirred at room temperature for 5 minutes and tert-butyl (((3S,5S)-5-(aminomethyl)-1-benzylpyrrolidin-3-yl)methyl)carbamate amine intermediate 2b (125 mg, 0.39 mmol) was added. The reaction was stirred at room temperature overnight. It was then diluted with EtOAc and washed with water and brine. The organic layer was dried over anhydrous sodium sulfate and filtered. The filtrate was concentrated under reduced pressure and purified on silica gel to give the product (150 mg, 63% yield) as a white solid. ¹H NMR (300 MHz, CDCl₃) δ 7.91 (m, 2H), 7.82 (m, 1H), 7.66-7.61 (m, 4H), 7.34-7.13 (m, 9H), 4.72 (m, 1H), 4.03 (d, J=13.2 Hz), 3.79 (m, 1H), 3.50 (m, 1H), 3.35 (d, J=13.5 Hz), 3.08 (m, 2H), 2.90-2.71 (m, 2H), 2.41 (m, 1H), 2.20 (m, 2H), 1.33 (s, 9H), 1.06 (m, 1H).

Example 6, Preparation of ((3R,5S)-5-(((4,4″-difluoro-[1,1′:3′,1″-terphenyl]-5′-yl)oxy)methyl)pyrrolidin-3-yl)methanamine dihydrochloride

Pd/C (10%, 20 mg) was added to a solution of tert-butyl (((3R,5S)-1-benzyl-5-(((4,4″-difluoro-[1,1′:3′,1″-terphenyl]-5′-yl)oxy)methyl)pyrrolidin-3-yl)methyl)carbamate (60 mg, 0.10 mmol) in methanol (10 mL). The reaction mixture was stirred under H₂ overnight. The solid was filtered off through a Celite pad and the filtrate was concentrated under reduced pressure to give a residue. The residue was dissolved in MeOH (2 mL). To this solution was added HCl solution in dioxane (4 N, 0.2 mL). The mixture was stirred at room temperature overnight then concentrated under reduced pressure. The crude product was triturated with EtOAc and the white solid was collected by filtration to provide the title compound (19 mg, 38% yield in two steps). ¹H NMR (300 MHz, DMSO) δ 9.70 (br, 1H), 9.60 (br, 1H), 8.15 (br, 3H), 7.84 (m, 4H), 7.50 (s, 1H), 7.30 (m, 4H), 7.24 (d, J=1.2 Hz, 2H), 4.95 (br, 1H), 3.60-3.20 (m, 3H), 3.10-2.75 (m, 4H), 2.38 (m, 2H), 1.55 (m, 1H).

The requisite intermediates were prepared as described in the following paragraphs.

Step 1)

DIAD (0.1 ml, 0.5 mmol) was added to a solution of (5S)-1-benzyl-5-(hydroxymethyl)pyrrolidine-3-carbonitrile (90 mg, 0.42 mmol), triphenylphosphine (131 mg, 0.50 mmol) and 4,4″-difluoro-[1,1′:3′,1″-terphenyl]-5′-ol (141 mg, 0.50 mmol) in THF (5 mL) at 0° C. The reaction mixture was stirred at 0° C. and allowed to warm to room temperature. The reaction was monitored by TLC. After the reaction was completed, the reaction mixture was concentrated under reduced pressure and purified by column chromatography on silica gel by using 5-20% ethyl acetate in hexanes afforded the top spot (112 mg, colorless oil, 56% yield) as (3S,5S)-1-benzyl-5-(((4,4″-difluoro-[1,1′:3′,1″-terphenyl]-5′-yl)oxy)methyl)pyrrolidine-3-carbonitrile. ¹HNMR (300 MHz, CDCl₃) δ 7.50 (m, 4H), 7.31 (m, 6H), 7.14 (m, 4H), 6.97 (d, J=1.8 Hz, 2H), 4.43 (m, 1H), 3.63 (m, 2H), 3.24 (m, 1H), 3.10 (m, 1H), 2.89 (m, 1H), 2.54 (m, 1H), 2.36 (m, 1H), 2.21 (m, 1H), 2.18 (m, 1H). and the bottom spot (38 mg, colorless oil, 19% yield) as (3R,5S)-1-benzyl-5-(((4,4″-difluoro-[1,1′:3′, 1″-terphenyl]-5′-yl)oxy)methyl)pyrrolidine-3-carbonitrile. ¹H NMR (300 MHz, CDCl₃) δ 7.58 (m, 4H), 7.30 (m, 6H), 7.14 (m, 4H), 7.03 (d, J=1.8 Hz, 2H), 4.21-0.05 (m, 3H), 3.61 (d, J=13.5 Hz, 1H), 3.28-3.16 (m, 2H), 3.02 (m, 1H), 2.65 (m, 1H), 2.51 (m, 1H), 2.20 (m, 1H).

Step 2)

LAH (20 mg, 0.47 mmol) was added to a solution of ((3S,5S))-1-benzyl-5-(((4,4″-difluoro-[1,1′:3′,1″-terphenyl]-5′-yl)oxy)methyl)pyrrolidine-3-carbonitrile (112 mg, 0.23 mmol) in dry THF (5 mL) at 0° C. under N₂. The reaction mixture was stirred at 0° C. for 30 minutes then room temperature for 1 hour. Then the reaction mixture was cooled to 0° C. and slowly added H₂O (0.02 mL), 15% NaOH solution (0.02 mL), EtOAc, and H₂O (0.06 mL). After stirring at room temperature for 30 min, Na₂SO₄ was added. It was allowed to stir for 30 minutes then the solid was removed by passing the mixture through a Celite Pad. The filtrate was concentrated under reduced pressure to give a crude intermediate amine. The crude intermediate was not further purified and identified. It was directly used in next step. The above intermediate was dissolved in methylene chloride (3 mL) then Boc₂O (76 mg, 0.35 mmol) and TEA (0.07 mL, 0.46 mmol) were added. The reaction mixture was stirred at room temperature overnight. The reaction mixture was diluted with methylene chloride and washed with water, brine then dried over anhydrous sodium sulfate. The solvent was removed under reduced pressure and the residue was purified by column chromatography on silica gel. The desired product was collected (65 mg, 48% yield) as a white solid. ¹H NMR (300 MHz, CDCl₃) δ 7.57 (m, 4H), 7.30 (m, 6H), 7.13 (m, 4H), 7.03 (d, J=1.8 Hz, 2H), 4.59 (br, 1H), 4.48 (br, 1H), 3.67-3.47 (m, 2H), 3.27 (m, 1H), 3.08 (m, 2H), 2.93 (m, 1H), 2.22 (m, 1H), 1.97 (m, 2H), 1.80 (m, 1H), 1.40 (m, 9H).

Example 7, Preparation of (((3S,5S)-5-(((4,4″-difluoro-[1,1′:3′,1″-terphenyl]-5′-yl)oxy)methyl)pyrrolidin-3-yl)methanamine dihydrochloride

Pd/C (10%, 15 mg) was added to a solution of tert-butyl (((3S,5S)-1-benzyl-5-(((4,4″-difluoro-[1,1′:3′,1″-terphenyl]-5′-yl)oxy)methyl)pyrrolidin-3-yl)methyl)carbamate (30 mg, 0.05 mmol) in methanol (10 mL). It was stirred under H₂ overnight. The solid was filtered off through a Celite pad and the filtrate was concentrated under reduced pressure to give a residue. The residue was dissolved in MeOH (2 mL). HCl solution in dioxane (4 N, 0.2 mL) was then added and the reaction mixture was stirred at room temperature overnight. The reaction mixture was then concentrated under reduced pressure. The crude product was triturated with EtOAc and the off-white solid was collected by filtration to provide the title compound (14 mg, 39% yield in two steps). ¹HNMR (300 MHz, DMSO) δ 9.83 (br, 1H), 9.39 (br, 1H), 8.16 (br, 3H), 7.81 (m, 4H), 7.50 (s, 1H), 7.30 (m, 4H), 7.23 (d, J=1.2 Hz, 2H), 4.48-4.29 (m, 2H), 4.01 (m, 2H), 3.14-2.96 (m, 3H), 2.44-2.33 (m, 3H).

The requisite intermediate was prepared as described in the following paragraph.

LAH (10 mg, 0.24 mmol) was added to a solution of (3R,5S)-1-benzyl-5-(((4,4″-difluoro-[1,1′:3′,1″-terphenyl]-5′-yl)oxy)methyl)pyrrolidine-3-carbonitrile (38 mg, 0.08 mmol) in dry THF (2 mL) at 0° C. under N₂. The reaction mixture was stirred at 0° C. for 30 minutes then at room temperature for 1 hour. The reaction mixture was then cooled to 0° C. The reaction was terminated by the slow addition of H₂O (0.01 mL), 15% NaOH solution (0.01 mL), EtOAc, and H₂O (0.03 mL) at 0° C. After stirring at room temperature for 30 min Na₂SO₄ was added. The reaction mixture was allowed to stir for 30 minutes, then the solid was removed by passing a Celite pad. The filtrate was concentrated under reduced pressure to give the crude intermediate amine. The crude intermediate was not further purified or characterized. It was directly used in next step. The above intermediate was dissolved in methylene chloride (3 mL) then Boc₂O (26 mg, 0.12 mmol) and TEA (0.03 mL, 0.16 mmol) were added. The reaction mixture was stirred at room temperature overnight. The reaction mixture was diluted with methylene chloride and washed with water, brine then dried over anhydrous sodium sulfate. The solvent was removed under reduced pressure and the residue purified by column chromatography on silica gel. The desired product was collected (36 mg, 78% yield) as a white solid. ¹H NMR (300 MHz, CDCl₃) δ 7.57 (m, 4H), 7.29 (m, 6H), 7.13 (m, 4H), 7.03 (d, J=1.8 Hz, 2H), 5.46 (br, 1H), 4.24-4.03 (m, 3H), 3.38 (d, J=13.5 Hz, 1H), 3.27-2.96 (m, 4H), 2.78 (d, J=9.3 Hz, 1H), 2.46-2.28 (m, 3H), 1.40 (m, 9H).

Example 8, Preparation of ((2S,4S)-4-((4,4″-difluoro-[1,1′:3′,1″-terphenyl]-5′-yl)oxy)pyrrolidin-2-yl)methanamine

Pd/C (10%, 20 mg) was added to a solution of ((2S,4S)-1-benzyl-4-((4,4″-difluoro-[1,1′:3′,1″-terphenyl]-5′-yl)oxy)pyrrolidin-2-yl)methanamine (50 mg, 0.1 mmol) in methanol (10 mL). It was stirred under H₂ overnight. The solid was filtered off through a Celite pad and the filtrate was concentrated under reduced pressure to give a residue. The residue was triturated with methylene chloride to afford the title compound as an off-white solid (26 mg, 65% yield). ¹HNMR (300 MHz, CD₃OD) δ 7.68 (m, 4H), 7.37 (m, 1H), 7.21-7.10 (m, 6H), 5.15 (m, 1H), 3.55 (m, 1H), 3.37 (m, 1H), 3.25 (m, 1H), 3.02 (m, 2H), 2.45 (m, 1H), 1.94-1.89 (m, 1H).

The requisite intermediates were prepared as described in the following paragraphs.

Step 1)

DIAD (0.46 ml, 2.34 mmol) was added to a solution of (2S,4R)-methyl 1-benzyl-4-hydroxypyrrolidine-2-carboxylate (500 mg, 2.13 mmol), triphenylphosphine (613 mg, 2.34 mmol) and 4,4″-difluoro-[1,1′:3′,1″-terphenyl]-5′-ol (600 mg, 2.13 mmol) in THF (20 mL) at 0° C. It was stirred at 0° C. then allowed to warm to room temperature. The reaction was monitored by TLC. After the reaction was complete, it was concentrated under reduced pressure and purified on column chromatograph with silica gel using 20% ethyl acetate in hexanes to give crude product as a colorless oil (500 mg, 47% yield). ¹H NMR (300 MHz, CDCl₃) δ 7.53 (m, 4H), 7.34-7.20 (m, 6H), 7.13 (m, 4H), 6.95 (d, J=1.2 Hz, 2H), 4.90 (m, 1H), 4.05 (d, J=13.5 Hz, 1H), 3.72 (s, 3H), 3.64 (d, J=12.9 Hz, 1H), 3.41-3.30 (m, 2H), 2.84-2.66 (m, 2H), 2.35-2.26 (m, 1H).

Step 2)

LiBH₄ (32 mg, 1.46 mmol) was added to the solution of (2S,4S)-methyl 1-benzyl-4-((4,4″-difluoro-[1,1′:3′,1″-terphenyl]-5′-yl)oxy)pyrrolidine-2-carboxylate (365 mg, 0.73 mmol) in dry THF (6 mL). The reaction mixture was stirred at 80° C. for 1 hour then cooled to 0° C. Acetone (0.2 mL) was added slowly to the reaction mixture to quench the reaction. After stirring at room temperature for 30 minutes, the solvent was removed to give a residue. The residue was dissolved in EtOAc and washed with water, saturated NaHCO₃ and then brine. The organic layer was dried over anhydrous sodium sulfate and filtered. The filtrate was concentrated under reduced pressure to afford the crude product as a white solid (268 mg, 78% yield). The crude product was not further identified and directly used in next step.

Step 3)

DIAD (0.13 ml, 0.63 mmol) was added to a solution of ((2S,4S)-1-benzyl-4-((4,4″-difluoro-[1,1′:3′,1″-terphenyl]-5′-yl)oxy)pyrrolidin-2-yl)methanol (268 mg, 0.57 mmol), triphenylphosphine (164 mg, 0.63 mmol) and phthalimide (92 mg, 0.57 mmol) in THF (5 mL) at 0° C. The reaction mixture was stirred at 0° C. and allowed to warm to room temperature. The reaction was monitored by TLC. After the reaction was complete, it was concentrated under reduced pressure and purified by column chromatograph with silica gel using 50-90% ethyl acetate in hexanes to give crude product as an off-white solid (292 mg, 85% yield). ¹H NMR (300 MHz, CDCl₃) δ 7.80 (m, 2H), 7.64 (m, 2H), 7.51 (m, 4H), 7.38-7.20 (m, 6H), 7.13 (m, 4H), 6.82 (d, J=1.5 Hz, 2H), 4.80 (m, 1H), 4.25 (d, J=12.9 Hz, 1H), 4.01-3.88 (m, 2H), 3.48 (d, J=13.5 Hz, 1H), 3.22 (d, J=11.1 Hz, 1H), 3.07 (m, 1H), 2.64-2.58 (m, 1H), 2.45 (m, 1H), 2.20-2.11 (m, 1H).

Step 4)

Hydrazine monohydrate (0.38 mL, 4.9 mmol) was added to the solution of 2-(((2S,4S)-1-benzyl-4-((4,4″-difluoro-[1,1′:3′,1″-terphenyl]-5′-yl)oxy)pyrrolidin-2-yl)methyl)isoindoline-1,3-dione (292 mg, 0.49 mmol) in MeOH (10 mL). The mixture was stirred at 80° C. for 1 hour then cooled to room temperature. The solvent was removed and the residue was triturated with CH₂Cl₂. The white solid was removed by filtration and the filtrate was concentrated under reduced pressure and purified by silica gel column chromatography. Elution with EtOAc then 1% NH₃H₂O in 10% MeOH/CH₂Cl₂ afforded the the higher Rf compound (192 mg, 84% yield) as a white solid. ¹H NMR (300 MHz, CDCl₃) δ 7.56 (m, 4H), 7.38-7.20 (m, 6H), 7.14 (m, 4H), 6.98 (d, J=1.8 Hz, 2H), 4.87 (m, 1H), 4.08 (d, J=13.5 Hz, 1H), 3.35 (d, J=13.5 Hz, 1H), 3.33 (d, J=11.1 Hz, 1H), 2.97-2.69 (m, 3H), 2.62-2.45 (m, 2H), 2.10-2.00 (m, 1H).

Example 9, N-(((2R,4R)-4-(Aminomethyl)pyrrolidin-2-yl)methyl)-4,4″-bis(trifluoromethyl)-[1,1′:3′,1″-terphenyl]-5′-carboxamide hydrochloride salt

To a solution of tert-butyl (((3R,5S)-1-benzyl-5-((4,4″-bis(trifluoromethyl)-[1,1′:3′,1″-terphenyl]-5′-carboxamido)methyl)pyrrolidin-3-yl)methyl)carbamate (58 mg, 0.08 mmol) in methanol (15 mL) was added Pd/C (10%, 25 mg). The reaction mixture was stirred under H₂ overnight. The solid was filtered off through a Celite pad and the filtrate was condensed under reduced pressure to give a residue. The residue was dissolved in MeOH (2 mL) was added HCl solution in dioxane (4 M, 0.2 mL) and it was stirred at room temperature overnight then condensed under reduced pressure. The crude product was triturated with EtOAc and the white solid was collected by filtration to provide the title compound as white solid (27 mg, 56% yield). LC-MS: 522.35 (M+H⁺).

The requisite intermediates were prepared as follows:

Step 1)

To the mixture of 4,4″-bis(trifluoromethyl)-[1,1′:3′,1″-terphenyl]-5′-carboxylic acid (46 mg, 0.11 mmol), tert-butyl (((3R,5S)-5-(aminomethyl)-1-benzylpyrrolidin-3-yl)methyl)carbamate (30 mg, 0.09 mmol), HOBt (7.6 mg, 0.06 mmol), and EDC (22 mg, 0.11 mmol) in dry DMF (1.5 mL) was added DIPEA (0.033 mL, 0.19 mmol). The reaction mixture was stirred at room temperature overnight. It was diluted with EtOAc and washed with water and brine. The organic layer was dried over anhydrous sodium sulfate and filtered. The filtrate was concentrated under reduced pressure and purified by column chromatography on silica gel using 50% EtOAc in hexane to give the product (60 mg, 89% yield) as a white solid. LC-MS: 712.35 (M+H⁺).

Step 2)

The mixture of methyl 2-(3, 5-dibromophenyl)-2-methylpropanoate (441 mg, 1.5 mmol) in 1,4-dioxane (20 mL) 2 N Na₂CO₃ (5.0 mL), (4-(trifluoromethyl)phenyl)boronic acid (627 mg, 3.3 mmol), tetrakis(triphenyl-phosphine)palladium (0.2 g) was degassed with N₂, then heated to reflux overnight. The cooled reaction mixture was worked up with ethyl acetate (60 mL) and brine (30 mL×2) to give a dark paste. The paste was purified on ISCO (40 g) with ethyl acetate (0˜10%)/hexanes to give the product as a light yellow solid. The solid was dissolved into THF/H₂O (15 mL:5 mL) and LiOH—H₂O (0.27 g, 6.4 mmol), and stirred at 50° C. for 10 hours. The reaction mixture was concentrated under reduced pressure and acidified with 1N HCl, The white solid was collected by filtration and dried to give the product 4,4″-bis(trifluoromethyl)-[1,1′:3′,1″-terphenyl]-5′-carboxylic acid as a white solid (430 mg, 70% yield). ¹H NMR (DMSO, 300 MHz): δ 8.44 (m, 3H), 8.23 (m, 4H), 8.01 (m, 4H).

Example 10. Preparation of N-(((2S,4R)-4-(aminomethyl)pyrrolidin-2-yl)methyl)-2-(4,4″-difluoro-[1,1′:3′,1″-terphenyl]-5′-yl)-2-methylpropanamide hydrochloride salt

To a solution of tert-butyl (((3R,5S)-1-benzyl-5-((2-(4,4″-difluoro-[1,13′,1″-terphenyl]-5′-yl)-2-methylpropanamido)methyl)pyrrolidin-3-yl)methyl)carbamate (50 mg, 0.08 mmol) in methanol (15 mL) was added Pd/C (10%, 25 mg). It was stirred under H₂ overnight. The solid was filtered off through a Celite pad and the filtrate was concentrated under reduced pressure to give a residue. The residue was dissolved in MeOH (2 mL) was added HCl solution in dioxane (4 M, 0.2 mL) and it was stirred at room temperature for 1 hour then concentrated under reduced pressure. The crude product was triturated with EtOAc and the off-white solid was collected by filtration to provide the title compound (23 mg, 46% yield in two steps). LC-MS: 464.35 (M+H⁺).

The requisite intermediate was prepared as follows:

Step 1)

To the mixture of 2-(4,4″-difluoro-[1,1′:3′,1″-terphenyl]-5′-yl)-2-methylpropanoic acid (40 mg, 0.11 mmol), tert-butyl (((3R,5S)-5-(aminomethyl)-1-benzylpyrrolidin-3-yl)methyl)carbamate (30 mg, 0.09 mmol), HOBt (7.6 mg, 0.06 mmol), and EDC (22 mg, 0.11 mmol) in dry DMF (1.5 mL) was added DIPEA (0.033 mL, 0.19 mmol). The reaction mixture was stirred at room temperature overnight. It was diluted with EtOAc and washed with water and brine. The organic layer was dried over anhydrous sodium sulfate and filtered. The filtrate was concentrated under reduced pressure and purified by column chromatography on silica gel using 50% EtOAc in hexanes to give the product (51 mg, 84% yield) as a white solid. LC-MS: 654.40 (M+H⁺).

Example 11. Preparation of N-(((2S,4S)-4-(aminomethyl)-1-methylpyrrolidin-2-yl)methyl)-4,4″-difluoro-[1,1′:3′,1″-terphenyl]-5′-carboxamide hydrochloride salt

To a solution of tert-butyl (((3S,5S)-5-((4,4″-difluoro-[1,1′:3′,1″-terphenyl]-5′-carboxamido) methyl)-1-methylpyrrolidin-3-yl)methyl)carbamate (20 mg, 0.04 mmol) in methanol (1 mL) was added HCl solution in dioxane (4 M, 0.2 mL) and the mixture was stirred at room temperature for 1 hour then concentrated under reduced pressure. The crude product was triturated with EtOAc and the off-white solid was collected by filtration to provide the title compound (15 mg, 71% yield) as white solid. LC-MS: 436.35 (M+H⁺).

The requisite intermediates were prepared as follows:

Step 1)

To a solution of tert-butyl (((3R,5S)-5-((4,4″-difluoro-[1,1′:3′,1″-terphenyl]-5′-carboxamido)methyl)pyrrolidin-3-yl)methyl)carbamate (40 mg, 0.08 mmol), 37% formaldehyde (0.031 mL, 0.38 mmol) in MeOH (5 mL) was added molecular sieve and sodium cyanoborohydride (80 mg, 0.38 mmol). The reaction mixture was stirred at room temperature overnight after molecular sieve was filtered off and was washed with EtOAc. The combined organic layers was washed with sodium bicarbonate and brine, dried over sodium sulfate and concentrated under reduced pressure to give a crude product. The crude product was purified by column chromatography on silica gel using EtOAc to afford the product (28 mg, 68% yield) as a white solid. LC-MS 536.35 (M+H⁺).

Step 2)

To a solution of tert-butyl (((3S,5S)-1-benzyl-5-((4,4″-difluoro-[1,1′:3′,1″-terphenyl]-5′-carboxamido)methyl)pyrrolidin-3-yl)methyl)carbamate (100 mg, 0.16 mmol) in methanol (15 mL) was added Pd/C (10%, 50 mg). It was stirred under H₂ overnight. The solid was filtered off through a Celite pad and the filtrate was concentrated under reduced pressure to give a residue which was purified on silica gel column. Elution with 10% MeOH/EtOAc afforded the desired product (62 mg, 73% yield). LC-MS: 522.35 (M+H⁺).

Example 12, Preparation of N-(((2S,4R)-4-((dimethylamino)methyl)pyrrolidin-2-yl)methyl)-4,4″-difluoro-[1,1′:3′,1″-terphenyl]-5′-carboxamide hydrochloride salt

To a solution of N-(((2S,4S)-1-benzyl-4-((dimethylamino)methyl)pyrrolidin-2-yl)methyl)-4,4″-difluoro-[1,1′:3′,1″-terphenyl]-5′-carboxamide (34 mg, 0.06 mmol) in methanol (10 mL) was added Pd/C (10%, 20 mg). It was stirred under H₂ overnight. The solid was filtered off through a Celite pad and the filtrate was concentrated under reduced pressure to give a residue. The residue was dissolved in MeOH (2 mL) was added HCl solution in dioxane (4 M, 0.2 mL) and it was stirred at room temperature for 1 hour then concentrated under reduced pressure. The crude product was triturated with EtOAc and the off-white solid was collected by filtration to provide the title compound (21 mg, 64% yield in two steps). ¹H NMR (CDCl₃, 300 MHz) δ 7.9 (s, 2H), 7.78 (s, 1H), 7.64-7.59 (m, 4H), 7.26 (s, 2H), 7.19-7.13 (m, 4H), 6.9 (bs, 1H), 3.85 (m, 1H), 3.3 (m, 1H), 2.98 (m, 1H), 2.7-2.01 (m, 13H).

The requisite intermediates were prepared as follows:

Step 1)

To a solution of N-(((2S,4S)-4-(aminomethyl)-1-benzylpyrrolidin-2-yl)methyl)-4,4″-difluoro-[1,1′:3′,1″-terphenyl]-5′-carboxamide (80 mg, 0.16 mmol), 37% formaldehyde (0.031 mL, 0.38 mmol) in MeOH (5 mL) was added molecular sieves and sodium cyanoborohydride (80 mg, 0.38 mmol). The reaction mixture was stirred at room temperature overnight after molecular sieve was filtered off and was washed with EtOAc. The combined organic layers was washed with sodium bicarbonate, brine, dried over sodium sulfate and concentrated under reduced pressure to give the crude product. The crude product was purified by column chromatography on silica gel using EtOAc to afford the product (56 mg, 67% yield) as a white solid. ¹H NMR (CDCl₃, 300 MHz) δ 7.95 (s, 2H), 7.82 (s, 1H), 7.64-7.61 (m, 4H), 7.4-7.17 (m, 1H), 4.14 (d, 1H), 3.84 (m, 1H), 3.49 (m, 2H), 3.14 (m, 1H), 2.84 (m, 1H), 2.6 (m, 1H), 2.45-2.10 (m, 10H).

Step 2)

To a solution of tert-butyl (((3S,5S)-1-benzyl-5-((4,4″-difluoro-[1,1′:3′,1″-terphenyl]-5′-carboxamido)methyl)pyrrolidin-3-yl)methyl)carbamate (150 mg, 0.25 mmol) in methanol (15 mL) was added HCl solution in dioxane (4 M, 0.5 mL) and it was stirred at room temperature for 1 hour then concentrated under reduced pressure. The residue was dissolved with EtOAc, washed with IN NaOH solution, brine, and dried over Na₂SO₄. The solvent was removed to give a desired product (110 mg, 88% yield). ¹H NMR (CDCl₃, 300 MHz) δ 7.30 (s, 2H), 7.18 (s, 1H), 7.10-6.93 (m, 5H), 6.60-6.50 (m, 10H), 2.38 (d, 1H), 3.15 (m, 1H), 2.86 (m, 1H), 2.6 (d, 1H), 2.3-1.6 (m, 8H).

Example 13, Preparation of N-(((3R,5R)-5-(aminomethyl)pyrrolidin-3-yl)methyl)-4,4″-difluoro-[1,1′:3′,1″-terphenyl]-5′-carboxamide hydrochloride salt

To a solution of N-(((3S,5S)-1-benzyl-5-(((2-oxo-2-phenyl-1λ²-ethyl)amino)methyl)pyrrolidin-3-yl)methyl)-4,4″-difluoro-[1,1′:3′,1″-terphenyl]-5′-carboxamide (50 mg, 0.08 mmol) in methanol (15 mL) was added Pd/C (10%, 50 mg). It was stirred under H₂ overnight. The solid was filtered off through a Celite pad and the filtrate was concentrated under reduced pressure to give a residue. The residue was dissolved in MeOH (2 mL) was added HCl solution in dioxane (4 M, 0.2 mL) and it was stirred at room temperature for 1 hour then concentrated under reduced pressure. The crude product was triturated with EtOAc and the off-white solid was collected by filtration to provide the title compound (19 mg, 48% yield in two steps). ¹H NMR (MeOD, 300 MHz) δ 8.05 (s, 2H), 8.00 (s, 1H), 7.81 (m, 4H), 7.22 (m, 4H), 3.98 (m, 1H), 3.61-3.2 (m, 6H), 2.84 (m, 2H), 2.45 (m, 1H), 1.71 (m, 1H).

The requisite intermediates were prepared as follows:

Step 1)

To the mixture of 4,4″-difluoro-[1,1′:3′,1″-terphenyl]-5′-carboxylic acid (33 mg, 0.11 mmol), 2-((((2S,4S)-4-(aminomethyl)-1-benzylpyrrolidin-2-yl)methyl)amino)-1-phenyl-2λ²-ethan-1-one (35 mg, 0.1 mmol), HOBt (7.6 mg, 0.06 mmol), and EDC (22 mg, 0.11 mmol) in dry DMF (1.5 mL) was added DIPEA (0.033 mL, 0.19 mmol). The reaction mixture was stirred at room temperature overnight. It was diluted with EtOAc and washed with water and brine. The organic layer was dried over anhydrous sodium sulfate and filtered. The filtrate was concentrated under reduced pressure and purified by column chromatography on silica gel using 50% EtOAc in hexane to give the product (50 mg, 79% yield) as a white solid. LC-MS: 646.40 (M+H⁺).

Step 2)

To a solution of/c/T-butyl (((3S,5S)-5-(aminomethyl)-1-benzylpyrrolidin-3-yl)methyl)carbamate (165 mg, 0.52 mmol) in CH₂Cl₂ (2 mL) was added benzyl carbonochloridate (0.09 mL, 0.63 mmol), and TEA (0.11 mL). The above mixture was stirred at room temperature for 2 hours. The solvent was removed and the residue purified by column chromatography on silica gel. The pure fractions were collected and concentrated under reduced pressure. The residue was dissolved in MeOH (5 mL). To the solution was added 4 N HCl in dioxane (0.5 mL). After stirring at room temperature for 4 hours, the solvent was removed and the residue was dissolved EtOAc. The organic solution was washed with 1 N NaOH solution, brine, dried over Na₂SO₄ and filtered. The filtrate was concentrated under reduced pressure to give the desired product (125 mg, 72% yield) used as such without further purification for the next step.

Example 14, Preparation of 4,4″-difluoro-N-(((2S,4R)-4-((methylamino)methyl)pyrrolidin-2-yl)methyl)-[1,1′:3′,1″-terphenyl]-5′-carboxamide hydrochloride salt

To a solution of tert-butyl (((3S,5S)-1-benzyl-5-((4,4″-difluoro-[1,1′:3′,1″-terphenyl]-5′-carboxamido)methyl)pyrrolidin-3-yl)methyl)(methyl)carbamate (40 mg, 0.06 mmol) in methanol (10 mL) was added Pd/C (10%, 25 mg). It was stirred under H₂ overnight. The solid was filtered off through a Celite pad and the filtrate was concentrated under reduced pressure to give a residue. The residue was dissolved in MeOH (2 mL) was added HCl solution in dioxane (4 M, 0.2 mL) and it was stirred at room temperature for 1 hour then concentrated under reduced pressure. The crude product was triturated with EtOAc and the off-white solid was collected by filtration to provide the title compound (16 mg, 50% yield in two steps). ¹H NMR (MeOD, 300 MHz) δ 9.15 (bs, 1H), 8.15 (s, 2H), 8.02 (s, 1H), 7.76 (m, 4H), 7.2 (m, 4H), 4.01 (m, 1H), 3.82 (m, 2H), 3.6 (m, 2H), 3.3 (m, 3H), 2.74 (s, 3H), 2.58 (m, 1H), 1.7 (m, 1H). LC-MS: 436.30 (M+H⁺).

The requisite intermediates were prepared as follows:

Step 1)

To the mixture of 4,4″-difluoro-[1,1′:3′,1″-terphenyl]-5′-carboxylic acid (30 mg, 0.09 mmol), tert-butyl (((3S,5S)-5-(aminomethyl)-1-benzylpyrrolidin-3-yl)methyl)(methyl)carbamate (31 mg, 0.1 mmol), HOBt (7.6 mg, 0.06 mmol), and EDC (22 mg, 0.11 mmol) in dry DMF (1.5 mL) was added DIPEA (0.033 mL, 0.19 mmol). The reaction mixture was stirred at room temperature overnight. It was diluted with EtOAc and washed with water and brine. The organic layer was dried over anhydrous sodium sulfate and filtered. The filtrate was concentrated under reduced pressure and purified by column chromatography on silica gel using 50% EtOAc in hexane to give the product (43 mg, 77% yield) as off-white solid. LC-MS: 626.40 (M+H⁺).

Step 2)

To a solution of tert-butyl (((3S,5S)-1-benzyl-5-(hydroxymethyl)pyrrolidin-3-yl)methyl)(methyl)carbamate (334 mg, 1.0 mmol), triphenylphosphine (288 mg, 1.1 mmol) and phthalimide (162 mg, 1.1 mmol) in THF (10 mL) was added DIAD (0.22 mL, 1.1 mmol) at 0° C. It was stirred at 0° C.-room temperature and monitored by TLC. After the reaction it was complete, it was concentrated under reduced pressure and purified on column chromatography with silica gel using 10-50% ethyl acetate in hexanes to give a crude product as an off-white solid (590 mg, ˜80% purity). To the solution of the above crude product (590 mg, ˜80% purity, ˜1.0 mmol) in MeOH (20 mL) was added hydrazine monohydrate (0.26 mL, 5.0 mmol). The mixture was stirred at 80° C. for 1 h then cooled to room temperature. The solvent was removed and the residue triturated with CH₂Cl₂. The white solid was removed by filtration and the filtrate concentrated under reduced pressure and purified by column chromatography on silica gel. Elution with EtOAc then 1% NH₃.H₂O in 10% MeOH/CH₂Cl₂ afforded the desired product as a light yellow oil which was used as crude intermediate in the next step.

Step 3)

To a solution of tert-butyl (((3R,5S)-1-benzyl-5-(hydroxymethyl)pyrrolidin-3-yl)methyl)carbamate (800 mg, 2.49 mmol) in dry THF (20 mL) at 0° C. under N₂ was added LAH (142 mg., 3.74 mmol) in several portions. The reaction mixture was stirred at 0° C. for 30 minutes, then 60° C. for 1 hour. The reaction mixture was cooled to 0° C. and H₂O (0.14 mL), 15% NaOH solution (0.14 mL), EtOAc, and H₂O (0.42 mL) were slowly added. After stirring at room temperature for 30 min, Na₂SO₄ was added. The reaction was allowed to stir for 30 minutes and the solid removed by passing a Celite pad. The filtrate was concentrated under reduced pressure to give a crude intermediate ((2S,4R)-1-benzyl-4-((methylamino)methyl)pyrrolidin-2-yl)methanol. The crude intermediate was not further purified. It was directly used in next step. The above intermediate was dissolved in methylene chloride (30 mL) then it was added Boc₂O (597 mg, 2.74 mmol) and TEA (0.52 mL, 3.74 mmol). The reaction mixture was stirred at room temperature overnight. The reaction mixture was diluted with methylene chloride and washed with water, brine then dried over anhydrous sodium sulfate. The solvent removed and the residue was purified by column chromatography on silica gel using EtOAc. The desired product was collected (364 mg, 44% yield in two steps) as colorless oil used as crude for the next steps.

Example 15. Description of General Methods Intrinsic MIC Assays

MIC assays were conducted in accordance with Clinical and Laboratory Standards Institute (CLSI) guidelines for broth microdilution. A 96-well plate containing cation-adjusted Mueller-Hinton (CAMH broth with 2-fold serial dilution of compounds was inoculated with log-phase bacterial at 5×10⁵ CFU/mL. The final volume in each well was 100 μL. Each compound was tested in duplicate. The microtiter plates were incubated in an aerobic environment for 18 hours at 37° C. Then the bacterial growth was tested by reading the plate with a VersaMax plate reader (Molecular Devices, Inc.) at 600 nm. The MIC was defined as the lowest compound concentration that inhibited 90% of bacteria growth.

The intrinsic MIC of the experimental EPIs was tested with the method described. The 2-fold serial dilution begin with 100 μg/mL of tested compound in the first column of the 96-well plates.

The following Gram-negative bacterial strains were included in these assays:

Escherichia coli ATCC 25922

Klebsiella pneumoniae ATCC 13883 and ATCC 10031

Pseudomonas aeruginosa ATCC 27853.

Acinetobacter baumannii ATCC 19606

Bacterial EPI Assays Tier 1 Testing

The EPI assay for the purposes of these studies represents a MIC assay in which the MIC of the antibiotic against the bacteria is tested in the presence of an experimental efflux pump inhibitor (EPI). The highest concentration of the EPI present in the assay typically is 14 of the intrinsic MIC of the compound. If the intrinsic MIC of the EPI is greater than 100 μg/mL, the EPI assay was tested with 50 μg/mL. Using serial dilutions of the EPI, its enhancement of antibiotic activity was then evaluated. The relative EPI activity was decided by comparing the MIC of the antibiotic in the presence of the EPI compound with the intrinsic MIC of the antibiotic alone. For the evaluation of the efficacy of an EPI against bacteria that were pre-exposed to an antibiotic, the inoculum of bacteria that used was developed from a bacterial culture isolated as a single colony following exposure at 14 the MIC of the antibiotic (so as to induce efflux pump expression), was to be used in combination with the EPI.

Example 16, Standard EPI Assays

The impact of Example 4 on the MIC values of two test antibiotics (levofloxacin and cefepime) against P. aeruginosa ATCC 27853 were evaluated using our standard EPI assay. Both levofloxacin and cefepime are known substrates of efflux pumps in P. aeruginosa, and are thus well-suited to be test antibiotics to assay for EPI activity.

The MIC of the test antibiotic is determined in the absence and presence of sub-inhibitory concentrations of the EPI. Initially, the sub-inhibitory concentration used was ½×MIC of the EPI. As the intrinsic MIC of Example 4 against P. aeruginosa ATCC 27853 is 12.5 μg/mL, we used 6.25 μg/mL (½×MIC) of the Example 4 in the standard EPI assay. The MIC of levofloxacin against P. aeruginosa ATCC 27853 in the absence of EPI is 1 μg/mL. In the presence of 6.25 μg/mL of the Example 4, the MIC of levofloxacin was markedly reduced to 0.016 μg/mL, a 64-fold reduction relative to the MIC of levofloxacin in the absence of EPI (1 μg/mL). When cefepime was used as the test antibiotic, the MIC of cefepime decreased by 16-fold, from 2 μg/mL in the absence of EPI to 0.125 μg/mL in the presence of 6.25 μg/mL of the Example 4. Similar methodology was employed to examine the synergy with Escherichia coli ATCC 25922 in the presence of varied concentrations of these EPIs using clarithromycin as the antibiotic.

Tier 2 Testing

A second tier of in vitro evaluation was performed for those compounds that exhibited EPI activity wherein bacteria were pre-exposed to the antibiotic at 14 of its MIC. This novel method of assessment provided a better prediction of those compounds that did demonstrate synergy with an antibiotic in vitro to demonstrate similar efficacy in vivo in mouse models of infection. These “Pre-exposure Bacterial EPI Assays” proved to be very effective method for prioritizing the selection of compounds for further assessment in vivo.

Example 17, Pre-Exposure Bacterial EPI Assays

For the Pre-exposure EPI assay, P. aeruginosa ATCC 27853 bacteria used in the assay were first grown in CAMH at 37° C. overnight in the presence of ½×MIC of the test antibiotic (cefepime or levofloxacin). The principle underlying this pre-exposure is that exposure of the bacteria to sub-inhibitory concentrations of the test antibiotic will induce expression of efflux pumps, if any, and may represent the scenario in vivo more accurately.

The MIC of cefepime against P. aeruginosa bacteria that have been pre-exposed to cefepime was determined to be 16 μg/mL, 8-fold higher than the MIC of cefepime against unexposed P. aeruginosa (2 μg/mL). The impact of Example 4 on the MIC of cefepime against pre-exposed bacteria was then assayed in a manner similar to the standard EPI assay described above, with the exception that pre-exposed bacteria were used to inoculate the 96-well plates. The MIC of cefepime against cefepime-exposed P. aeruginosa reduced from 16 μg/mL to 0.25 μg/mL in the presence of 6.25 μg/mL of the Example 4, a 64-fold reduction. This result indicates that Example 4 is able to inhibit the pump induced in bacteria that have been pre-exposed to cefepime.

Thus by using the Pre-exposure EPI assay, information regarding the ability of an EPI to inhibit efflux pumps induced upon exposure to different antibiotics can be gleaned. This information is valuable in directing in vivo experiments and predicting the efficacy of a particular EPI-antibiotic pair.

Example 18, Fluorescent-Based Cellular Assay for Efflux Inhibition

The impact of potential EPI compounds on the activity of efflux pumps was also evaluated with a fluorescence-based cellular assay that measures the efflux of Hoechst 33342, a known substrate of Gram-negative bacterial efflux pumps. When bound to intracellular bacterial DNA, Hoechst 33342 fluoresces brightly, while the unbound fluorophore outside the bacterial cell exhibits little or no fluorescence. Thus, the efflux of Hoechst 33342 from inside to outside the bacterial cell is associated with a substantive decrease in fluorescence.

Bacterial cells were harvested from overnight cultures by centrifugation, and the cell pellet was washed with phosphate-buffered containing 1 mM MgCl₂ (PBSM). After washing the cells, the cell pellets were resuspended in PBSM to achieve a final OD at 600 nm of 0.6 to 0.9. The ATP required for efflux pump function was then depleted by addition of carbonyl cyanide 3-chlorophenylhydrazone (CCCP) to a final concentration in the range of 3 to 10 μM. Hoechst 33342 was then added to a final concentration of 10 μM, and the cells were incubated aerobically at 37° C. for 0.5 to 18 hours. The bacterial suspension (200 μL) was added to wells of a black, flat-bottom 96-well plate containing test EPI compounds at concentrations of ranging from 1.6 to 25 μg/mL or an equivalent volume of the vehicle (DMSO) alone. A plate vortexer was used to mix the bacterial cells with the test EPI compounds, and the plates are pre-incubated at 37° C. for 5 minutes. After the pre-incubation, Hoechst 33342 efflux was initiated by addition of glucose to a final concentration of 10 to 50 mM. A SpectraMax® 2 fluorescent plate reader (Molecular Devices, Inc., Sunnyvale, Calif.) was used to monitor the fluorescence of each well at 37° C. once per minute for 20 to 60 minutes. The excitation and emission wavelengths were set at 355 and 460 nm, respectively. E. coli ATCC 25922, K. pneumoniae ATCC 13883, P. aeruginosa ATCC 27853, and Acinetobacter baumannii ATCC 19606 were used as model Gram-negative bacterial strains in this assay.

A general method for the in vivo assessment of bacterial EPIs is complicated by the fact that that both the antibiotic and the EPI need to be present for synergy to be achieved. A general method was discovered that has proven to be effective in establishing the relative efficacy of bacterial EPIs in a mouse septicemia model. The bacterial EPI is administered initially intravenously to mice with septicemia, followed 5 minutes later by the intravenous administration or oral administration of the antibiotic. A second administration of the EPI is then administered subcutaneously after an additional 5 minutes to act as a booster, followed by the final administration of the antibiotic either intravenously or orally after the second administration of the EPI. In many instances, this regiment has proved effective in demonstrating synergy and allowing survival of the infected mice. In a few instances, a second regiment of both EPI and antibiotic as administered on day 1 was required after 24 hours to affect cures.

Example 19. Methods of Assessment of In Vivo Efficacy of Efflux Pump Inhibitors

Determination of the in vivo efficacy of bacterial efflux pump inhibitors (EPIs) can be efficiently determined using a mouse septicemia model of infection. The systemic infection is initiated by a 500 ul intraperitoneal injection of an inoculum containing bacteria (such as P. aeruginosa [ATCC 27853]) at a concentration of approximately 5×10⁵ cells in 5% mucin in Swiss Webster female mice. The experimental groups (4-6 infected mice each) consist of both positive and negative controls, as well as infected mice treated with antibiotic alone or EPI alone, as well as the EPI administered in combination with the antibiotic. Five mutes post-infection an EPI is administered iv with an antibiotic such as cefepime (250 ul of a 10 mg/ml solution) being administered 10 minutes post-infection. A second dose of the EPI is then administered sc 20 minutes post-infection, with cefepime again being administered (250 ul of a 10 mg/ml solution) 25 minutes post-infection. Mice treated with cefepime alone were injected with an iv dose (250 ul of a 10 mg/ml solution) b.i.d. at 10 and 25 minutes post-infection. Mice treated with EPI alone were treated iv 5 minutes post infection and sc 20 minutes post-infection. Additional experimental groups consisting of 4-6 infected mice were untreated or treated with vehicle alone at the appropriate time points. If required, this regiment would be repeated 24 hours post-infection on day 2 of the assay.

% Survival % Survival* % Survival (24 hr) (72 hr) (72 hr) Vehicle Antibiotic Antibiotic + Experiment EPI Controls Only EPI #489 Example 4 0% 0%**** 100% *cefepime, 10 mg/ml b.i.d.; 250 ul; Example 4; 2.0 mg/ml b.i.d.

Example 14

The following can illustrate representative pharmaceutical dosage forms, containing a compound of formula I (‘Compound X’) or a pharmaceutically acceptable salt thereof, for therapeutic or prophylactic use in humans. The tablets can optionally comprise an enteric coating.

(i) Tablet 1 mg/tablet Compound X= 100.0 Lactose 77.5 Povidone 15.0 Croscarmellose sodium 12.0 Microcrystalline cellulose 92.5 Magnesium stearate 3.0 300.0 (ii) Tablet 2 mg/tablet Compound X= 20.0 Microcrystalline cellulose 410.0 Starch 50.0 Sodium starch glycolate 15.0 Magnesium stearate 5.0 500.0 (iii) Capsule mg/capsule Compound X= 10.0 Colloidal silicon dioxide 1.5 Lactose 465.5 Pregelatinized starch 120.0 Magnesium stearate 3.0 600.0 (iv) Injection 1 (1 mg/mL) mg/mL Compound X= (free acid form) 1.0 Dibasic sodium phosphate 12.0 Monobasic sodium phosphate 0.7 Sodium chloride 4.5 1.0N Sodium hydroxide solution (pH adjustment to 7.0-7.5) q.s. Water for injection q.s. ad 1 mL (v) Injection 2 (10 mg/mL) mg/mL Compound X= (free acid form) 10.0 Monobasic sodium phosphate 0.3 Dibasic sodium phosphate 1.1 Polyethylene glycol 400 200.0 1.0N Sodium hydroxide solution (pH adjustment to 7.0-7.5) q.s. Water for injection q.s. ad 1 mL (vi) Aerosol mg/can Compound X= 20.0 Oleic acid 10.0 Trichloromonofluoromethane 5,000.0 Dichlorodifluoromethane 10,000.0 Dichlorotetrafluoroethane 5,000.0

The above formulations may be obtained by conventional procedures well known in the pharmaceutical art.

All publications, patents, and patent documents are incorporated by reference herein, as though individually incorporated by reference. The invention has been described with reference to various specific and preferred embodiments and techniques. However, it should be understood that many variations and modifications may be made while remaining within the spirit and scope of the invention. 

1. A compound of formula I:

wherein: A is —C(═O)N(R^(a1))—R¹, —(C₁-C₃)alkyl-C(═O)N(R^(a1))R¹, —(C₁-C₃)alkyl-O —R¹, —O—R¹, —(C₁-C₃)alkyl-N(R^(a1))—R¹, or —N(R^(a1))—R¹; each R¹ is independently a (C₃-C₇)carbocyclyl, (C₃-C₇)carbocyclyl-(C₁-C₄)alkyl-, 4-7 membered monocyclic heterocyclyl, or 4-7 membered monocyclic heterocyclyl-(C₁-C₄)alkyl-, wherein each (C₃-C₇)carbocyclyl or (C₃-C₇)carbocyclyl-(C₁-C₄)alkyl- is independently substituted with one or more groups selected from the group consisting of Z and —(C₁-C₆)alkyl substituted with one or more Z, and wherein each 4-7 membered monocyclic heterocyclyl or 4-7 membered monocyclic heterocyclyl-(C₁-C₄)alkyl- is independently optionally substituted with one or more groups selected from the group consisting of Z and —(C₁-C₆)alkyl substituted with one or more Z, wherein each Z is independently selected from the group consisting of NR^(b2)R^(c2), —NHNH₂, —C(═NR^(a2))(NR^(b2)R^(c2)), —NR^(a2)C(═NR^(a2))(R^(d2)), and —NR^(a2)C(═NR^(a2))(NR^(b2)R^(c2)) and wherein each (C₃-C₇)carbocyclyl, (C₃-C₇)carbocyclyl-(C₁-C₄)alkyl-, 4-7 membered monocyclic heterocyclyl, or 4-7 membered monocyclic heterocyclyl-(C₁-C₄)alkyl-, is independently optionally substituted independently with one or more (C₁-C₄)alkyl; R² is hydrogen, halo, (C₁-C₄)alkyl, (C₁-C₄)haloalkyl, (C₁-C₄)alkoxy, (C₁-C₄)haloalkoxy, aryl or heteroaryl wherein the aryl or heteroaryl is optionally substituted with one or more groups independently selected from halo, —NO₂, —CN, (C₁-C₄)alkyl, (C₁-C₄)haloalkyl, (C₁-C₄)alkoxy and (C₁-C₄)haloalkoxy; R³ is hydrogen, halo, (C₁-C₆)alkyl, (C₁-C₄)haloalkyl, (C₁-C₆)alkoxy, (C₁-C₄)haloalkoxy, aryl or heteroaryl wherein the aryl or heteroaryl is optionally substituted with one or more groups independently selected from halo, —NO₂, —CN, (C₁-C₆)alkyl, (C₁-C₄)haloalkyl, (C₁-C₆)alkoxy and (C₁-C₄)haloalkoxy; R⁴ is hydrogen, halo, (C₁-C₆)alkyl, (C₁-C₄)haloalkyl, (C₁-C₆)alkoxy, (C₁-C₄)haloalkoxy, aryl or heteroaryl wherein the aryl or heteroaryl is optionally substituted with one or more groups independently selected from halo, —NO₂, —CN, (C₁-C₆)alkyl, (C₁-C₄)haloalkyl, (C₁-C₆)alkoxy and (C₁-C₄)haloalkoxy; R⁵ is hydrogen, halo, (C₁-C₆)alkyl, (C₁-C₄)haloalkyl, (C₁-C₆)alkoxy, (C₁-C₄)haloalkoxy, aryl or heteroaryl wherein the aryl or heteroaryl is optionally substituted with one or more groups independently selected from halo, —NO₂, —CN, (C₁-C₆)alkyl, (C₁-C₄)haloalkyl, (C₁-C₆)alkoxy and (C₁-C₄)haloalkoxy; R⁶ is hydrogen, halo, (C₁-C₄)alkyl, (C₁-C₄)haloalkyl, (C₁-C₄)alkoxy, (C₁-C₄)haloalkoxy, aryl or heteroaryl wherein the aryl or heteroaryl is optionally substituted with one or more groups independently selected from halo, —NO₂, —CN, (C₁-C₄)alkyl, (C₁-C₄)haloalkyl, (C₁-C₄)alkoxy and C₁-C₄)haloalkoxy; each R^(a1) is independently hydrogen, (C₁-C₆)alkyl or (C₃-C₇)carbocyclyl; each R^(a2) is independently hydrogen, (C₁-C₆)alkyl or (C₃-C₇)carbocyclyl; each R^(b2) and R^(c2) is independently hydrogen, (C₁-C₆)alkyl or (C₃-C₇)carbocyclyl; and R^(d2) is (C₁-C₆)alkyl or (C₃-C₇)carbocyclyl; or a salt thereof.
 2. The compound or salt of claim 1, wherein A is —C(═O)N(R^(a1))—R¹, —(C₁-C₃)alkyl-C(═O)N(R^(a1))R¹, —(C₁-C₃)alkyl-O —R¹, or —O—R¹.
 3. The compound or salt of claim 1, wherein A is —C(═O)N(R^(a1))—R¹.
 4. The compound or salt of claim 1, wherein A is —(C₁-C₃)alkyl-C(═O)N(R^(a1))R¹.
 5. The compound or salt of any one of claims 1-4, wherein R^(a1) is hydrogen.
 6. The compound or salt of claim 1, wherein A is —O—R¹.
 7. The compound or salt of any one of claims 1-6, wherein R² is hydrogen, halo, (C₁-C₄)alkyl, (C₁-C₄)haloalkyl, (C₁-C₄)alkoxy, or (C₁-C₄)haloalkoxy.
 8. The compound or salt of any one of claims 1-6, wherein R² is hydrogen.
 9. The compound or salt of any one of claims 1-8, wherein R³ is aryl or heteroaryl wherein the aryl or heteroaryl is optionally substituted with one or more groups independently selected from halo, —NO₂, —CN, (C₁-C₆)alkyl, (C₁-C₄)haloalkyl, (C₁-C₆)alkoxy and (C₁-C₄)haloalkoxy.
 10. The compound or salt of any one of claims 1-8, wherein R³ is phenyl wherein the phenyl is optionally substituted with one or more groups independently selected from halo, —NO₂, —CN, (C₁-C₆)alkyl, (C₁-C₄)haloalkyl, (C₁-C₆)alkoxy and (C₁-C₄)haloalkoxy.
 11. The compound or salt of any one of claims 1-8, wherein R³ is 4-fluorophenyl or 4-trifluoromethyphenyl.
 12. The compound or salt of any one of claims 1-6, wherein R⁴ is hydrogen, halo, (C₁-C₆)alkyl, (C₁-C₄)haloalkyl, (C₁-C₆)alkoxy, (C₁-C₄)haloalkoxy.
 13. The compound or salt of any one of claims 1-6, wherein R⁴ is hydrogen.
 14. The compound or salt of any one of claims 1-13, wherein R⁵ is aryl or heteroaryl wherein the aryl or heteroaryl is optionally substituted with one or more groups independently selected from halo, —NO₂, —CN, (C₁-C₆)alkyl, (C₁-C₄)haloalkyl, (C₁-C₆)alkoxy and (C₁-C₄)haloalkoxy.
 15. The compound or salt of any one of claims 1-13, wherein R⁵ is phenyl wherein the phenyl is optionally substituted with one or more groups independently selected from halo, —NO₂, —CN, (C₁-C₆)alkyl, (C₁-C₄)haloalkyl, (C₁-C₆)alkoxy and (C₁-C₄)haloalkoxy.
 16. The compound or salt of any one of claims 1-13, wherein R⁵ is 4-fluorophenyl or 4-trifluoromethyphenyl.
 17. The compound or salt of any one of claims 1-16, wherein R⁶ is hydrogen, halo, (C₁-C₄)alkyl, (C₁-C₄)haloalkyl, (C₁-C₄)alkoxy, or (C₁-C₄)haloalkoxy.
 18. The compound or salt of any one of claims 1-16, wherein R⁶ is hydrogen.
 19. The compound or salt of any one of claims 1-6, wherein the moiety:

of the compound of formula I is:


20. The compound or salt of any one of claims 1-17, wherein R¹ is a 4-7 membered monocyclic heterocyclyl or 4-7 membered monocyclic heterocyclyl-(C₁-C₄)alkyl-, wherein the 4-7 membered monocyclic heterocyclyl or 4-7 membered monocyclic heterocyclyl-(C₁-C₄)alkyl- is optionally substituted independently with one or more groups selected from the group consisting of Z and —(C₁-C₆)alkyl substituted with one or more Z, wherein each Z is NR^(b2)R^(c2)nd wherein the 4-7 membered monocyclic heterocyclyl or 4-7 membered monocyclic heterocyclyl-(C₁-C₄)alkyl- is optionally substituted with one or more (C₁-C₄)alkyl.
 21. The compound or salt of any one of claims 1-17, wherein R¹ is a 4-7 membered monocyclic N-heterocyclyl or 4-7 membered monocyclic N-heterocyclyl-(C₁-C₄)alkyl-, wherein the 4-7 membered monocyclic N-heterocyclyl or 4-7 membered monocyclic N-heterocyclyl-(C₁-C₄)alkyl- is optionally substituted independently with one or more groups selected from the group consisting of Z and —(C₁-C₆)alkyl substituted with one or more Z, wherein each Z is NR^(b2)R^(c2)nd wherein the 4-7 membered monocyclic N-heterocyclyl or 4-7 membered monocyclic N-heterocyclyl-(C₁-C₄)alkyl- is optionally substituted with one or more (C₁-C₄)alkyl.
 22. The compound or salt of any one of claims 1-17, wherein R¹ is a pyrrolidinyl or pyrrolidinyl-(C₁-C₄)alkyl-, wherein the pyrrolidinyl or pyrrolidinyl-(C₁-C₄)alkyl- is optionally substituted independently with one or more groups selected from the group consisting of Z and —(C₁-C₆)alkyl substituted with one or more Z, wherein each Z is NR^(b2)R^(c2)nd wherein the pyrrolidinyl or pyrrolidinyl-(C₁-C₄)alkyl-is optionally substituted with one or more (C₁-C₄)alkyl.
 23. The compound or salt of any one of claims 1-17, wherein R¹ is a pyrrolidinyl or pyrrolidinyl-(CH₂)—, wherein the pyrrolidinyl-(CH₂)— is optionally substituted independently with one or more groups selected from the group consisting of Z and —(C₁-C₆)alkyl substituted with one or more Z, wherein each Z is NR^(b2)R^(c2) and wherein the pyrrolidinyl or pyrrolidinyl-(C₁-C₄)alkyl-is optionally substituted with one or more (C₁-C₄)alkyl.
 24. The compound or salt of any one of claims 1-17, wherein R¹ is a pyrrolidinyl or pyrrolidinyl-(CH₂)—, wherein the pyrrolidinyl-(CH₂)— is optionally substituted independently with one or more groups selected from the group consisting of Z and —(C₁-C₄)alkyl substituted with one or more Z, wherein each Z is NR^(b2)R^(c2).
 25. The compound or salt of any one of claims 1-24, wherein each R^(b2) and R^(c2) is hydrogen or (C₁-C₆)alkyl
 26. The compound or salt of any one of claims 1-19, wherein R¹ is:


27. The compound or salt of claim 1, wherein A is:


28. The compound or salt of claim 1 that is:

or a salt thereof.
 29. The compound or salt of claim 1 that is


30. A pharmaceutical composition comprising a compound or a pharmaceutically acceptable salt thereof as described in any one of claims 1-29, and a pharmaceutically acceptable vehicle.
 31. A pharmaceutical composition comprising a compound or a pharmaceutically acceptable salt thereof as described in any one of claims 1-29, one or more antibacterial agents and a pharmaceutically acceptable vehicle.
 32. A method of inhibiting a bacterial efflux pump in an animal comprising administering to the animal a compound or a pharmaceutically acceptable salt thereof as described in any one of claims 1-29.
 33. A method of treating or preventing a bacterial infection in an animal comprising co-administering to the animal a compound or a pharmaceutically acceptable salt thereof as described in any one of claims 1-29 and one or more antibacterial agents.
 34. The method of claim 32 or claim 33 wherein the animal has a bacterial infection.
 35. The method of claim 33 or 34 wherein the bacterial infection is a Gram-negative bacterial strain infection.
 36. The method of claim 35, wherein the Gram-negative bacterial strain is selected from the group consisting of Acinetobacter baumannii, Acinetobacter calcoaceticus, Acinetobacter haemolyticus, Acinetobacter lwoffi, Actinobacillus actinomycetemcomitans, Aeromonas hydrophilia, Aggregatibacter actinomycetemcomitans, Agrobacterium tumefaciens, Bacteroides distasonis, Bacteroides eggerthii, Bacteroides forsythus, Bacteroides fragilis, Bacteroides ovalus, Bacteroides splanchnicus, Bacteroides thetaiotaomtcron, Bacteroides uniformis, Bacteroides vulgatus, Bordetella bronchiseptica, Bordetella parapertussis, Bordetella pertussis, Borrelia burgdorferi, Branhamella catarrhalis, Burkholderia cepacia, Campylobacter coli, Campylobacter fetus, Campylobacter jejuni, Caulobacter crescentus, Chlamydia trachomatis, Citrobacter diversus, Citrobacter freundii, Enterobacter aerogenes, Enterobacter asburiae, Enterobacter cloacae, Enterobacter sakazakii, Escherchia coli, Francisella tularensis, Fusobacterium nucleatum, Gardnerella vaginalis, Haemophilus ducreyi, Haemophilus haemolyticus, Haemophilus influenzae, Haemophilus parahaemolyticus, Haemophilus parainfluenzae, Helicobacter pylori, Kingella denitrificans, Kingella indologenes, Kingella kingae, Kingella oralis, Klebsiella oxytoca, Klebsiella pneumoniae, Klebsiella rhinoscleromatis, Legionella pneumophila, Listeria monocytogenes, Moraxella bovis, Moraxella catarrhalis, Moraxella lacunata, Morganella morganaii, Neisseria gonorrhoeae, Neisseria meningitidis, Pantoea agglomerans, Pasteurella cams, Pasteurella haemolytica, Pasteurella multocida, Pasteurella tularensis, Porphyromonas gingivalis, Proteus mirabilis, Proteus vulgaris, Providencia alcalifaciens, Providencia rettgeri, Providencia stuartii, Pseudomonas acidovorans, Pseudomonas aeruginosa, Pseudomonas alcaligenes, Pseudomonas fluorescens, Pseudomonas putida, Salmonella enteriditis, Salmonella paratyphi, Salmonella typhi, Salmonella typhimurium, Serratia marcescens, Shigella dysenteriae, Shigella jlexneri, Shigella sonnet, Stenotrophomonas maltophilla, Veillonella parvula, Vibrio cholerae, Vibrio parahaemolyticus, Yersinia enterocolitica, Yersinia intermedia, Yersinia pestis and Yersinia pseudotuberculosis.
 37. The method of claim 33 or 34, wherein the bacterial infection is a Gram-positive bacterial strain infection.
 38. The method of claim 37, wherein the Gram-positive bacterial strain is selected from the group consisting of Actinomyces naeslundii, Actinomyces viscosus, Bacillus anthracis, Bacillus cereus, Bacillus subtilis, Clostridium difficile, Corynebacterium diphtheriae, Corynebacterium ulcerans, Enterococcus faecalis, Enterococcus faecium, Micrococcus luteus, Mycobacterium avium, Mycobacterium intracellulare, Mycobacterium leprae, Mycobacterium tuberculosis, Propionibacterium acnes, Staphylococcus aureus, Staphylococcus epidermidis, Staphylococcus haemolyticus, Staphylococcus hominis, Staphylococcus hyicus, Staphylococcus intermedius, Staphylococcus saccharolyticus, Staphylococcus saprophyticus, Streptococcus agalactiae, Streptococcus mutans, Streptococcus pneumoniae, Streptococcus pyogenes, Streptococcus salivarius and Streptococcus sanguis.
 39. A compound or a pharmaceutically acceptable salt thereof as described in any one of claims 1-29 for use in medical treatment.
 40. A compound or a pharmaceutically acceptable salt thereof as described in any one of claims 1-29 for the prophylactic or therapeutic inhibition of a bacterial efflux pump for the treatment of a bacterial infection.
 41. A compound or a pharmaceutically acceptable salt thereof as described in any one of claims 1-29 which is used in combination with one or more antibacterial agents for the prophylactic or therapeutic treatment of a bacterial infection.
 42. The use of a compound or a pharmaceutically acceptable salt thereof as described in any one of claims 1-29 for the preparation of a medicament for inhibiting a bacterial efflux pump.
 43. The use of a compound or a pharmaceutically acceptable salt thereof as described in any one of claims 1-29 for the preparation of a medicament for treating a bacterial infection in an animal.
 44. The use of a compound or a pharmaceutically acceptable salt thereof as described in any one of claims 1-29 and one or more antibacterial agents for the preparation of a medicament for treating a bacterial infection in an animal. 